diff options
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 414 |
1 files changed, 243 insertions, 171 deletions
diff --git a/fs/namei.c b/fs/namei.c index 3f1829b3ab5b..8533087e5dac 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -22,6 +22,7 @@ #include <linux/fs.h> #include <linux/namei.h> #include <linux/pagemap.h> +#include <linux/sched/mm.h> #include <linux/fsnotify.h> #include <linux/personality.h> #include <linux/security.h> @@ -566,7 +567,7 @@ struct nameidata { struct path root; struct inode *inode; /* path.dentry.d_inode */ unsigned int flags, state; - unsigned seq, m_seq, r_seq; + unsigned seq, next_seq, m_seq, r_seq; int last_type; unsigned depth; int total_link_count; @@ -664,6 +665,13 @@ static void drop_links(struct nameidata *nd) } } +static void leave_rcu(struct nameidata *nd) +{ + nd->flags &= ~LOOKUP_RCU; + nd->seq = nd->next_seq = 0; + rcu_read_unlock(); +} + static void terminate_walk(struct nameidata *nd) { drop_links(nd); @@ -677,8 +685,7 @@ static void terminate_walk(struct nameidata *nd) nd->state &= ~ND_ROOT_GRABBED; } } else { - nd->flags &= ~LOOKUP_RCU; - rcu_read_unlock(); + leave_rcu(nd); } nd->depth = 0; nd->path.mnt = NULL; @@ -729,13 +736,6 @@ static bool legitimize_links(struct nameidata *nd) static bool legitimize_root(struct nameidata *nd) { - /* - * For scoped-lookups (where nd->root has been zeroed), we need to - * restart the whole lookup from scratch -- because set_root() is wrong - * for these lookups (nd->dfd is the root, not the filesystem root). - */ - if (!nd->root.mnt && (nd->flags & LOOKUP_IS_SCOPED)) - return false; /* Nothing to do if nd->root is zero or is managed by the VFS user. */ if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET)) return true; @@ -771,14 +771,13 @@ static bool try_to_unlazy(struct nameidata *nd) BUG_ON(!(nd->flags & LOOKUP_RCU)); - nd->flags &= ~LOOKUP_RCU; if (unlikely(!legitimize_links(nd))) goto out1; if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) goto out; if (unlikely(!legitimize_root(nd))) goto out; - rcu_read_unlock(); + leave_rcu(nd); BUG_ON(nd->inode != parent->d_inode); return true; @@ -786,7 +785,7 @@ out1: nd->path.mnt = NULL; nd->path.dentry = NULL; out: - rcu_read_unlock(); + leave_rcu(nd); return false; } @@ -794,24 +793,27 @@ out: * try_to_unlazy_next - try to switch to ref-walk mode. * @nd: nameidata pathwalk data * @dentry: next dentry to step into - * @seq: seq number to check @dentry against * Returns: true on success, false on failure * - * Similar to to try_to_unlazy(), but here we have the next dentry already + * Similar to try_to_unlazy(), but here we have the next dentry already * picked by rcu-walk and want to legitimize that in addition to the current * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context. * Nothing should touch nameidata between try_to_unlazy_next() failure and * terminate_walk(). */ -static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsigned seq) +static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry) { + int res; BUG_ON(!(nd->flags & LOOKUP_RCU)); - nd->flags &= ~LOOKUP_RCU; if (unlikely(!legitimize_links(nd))) goto out2; - if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) - goto out2; + res = __legitimize_mnt(nd->path.mnt, nd->m_seq); + if (unlikely(res)) { + if (res > 0) + goto out2; + goto out1; + } if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref))) goto out1; @@ -824,7 +826,7 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi */ if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) goto out; - if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) + if (read_seqcount_retry(&dentry->d_seq, nd->next_seq)) goto out_dput; /* * Sequence counts matched. Now make sure that the root is @@ -832,7 +834,7 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi */ if (unlikely(!legitimize_root(nd))) goto out_dput; - rcu_read_unlock(); + leave_rcu(nd); return true; out2: @@ -840,10 +842,10 @@ out2: out1: nd->path.dentry = NULL; out: - rcu_read_unlock(); + leave_rcu(nd); return false; out_dput: - rcu_read_unlock(); + leave_rcu(nd); dput(dentry); return false; } @@ -968,7 +970,7 @@ static int nd_jump_root(struct nameidata *nd) d = nd->path.dentry; nd->inode = d->d_inode; nd->seq = nd->root_seq; - if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq))) + if (read_seqcount_retry(&d->d_seq, nd->seq)) return -ECHILD; } else { path_put(&nd->path); @@ -984,7 +986,7 @@ static int nd_jump_root(struct nameidata *nd) * Helper to directly jump to a known parsed path from ->get_link, * caller must have taken a reference to path beforehand. */ -int nd_jump_link(struct path *path) +int nd_jump_link(const struct path *path) { int error = -ELOOP; struct nameidata *nd = current->nameidata; @@ -1031,7 +1033,7 @@ static struct ctl_table namei_sysctls[] = { .procname = "protected_symlinks", .data = &sysctl_protected_symlinks, .maxlen = sizeof(int), - .mode = 0600, + .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, @@ -1040,7 +1042,7 @@ static struct ctl_table namei_sysctls[] = { .procname = "protected_hardlinks", .data = &sysctl_protected_hardlinks, .maxlen = sizeof(int), - .mode = 0600, + .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, @@ -1049,7 +1051,7 @@ static struct ctl_table namei_sysctls[] = { .procname = "protected_fifos", .data = &sysctl_protected_fifos, .maxlen = sizeof(int), - .mode = 0600, + .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_TWO, @@ -1058,7 +1060,7 @@ static struct ctl_table namei_sysctls[] = { .procname = "protected_regular", .data = &sysctl_protected_regular, .maxlen = sizeof(int), - .mode = 0600, + .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_TWO, @@ -1176,7 +1178,7 @@ static bool safe_hardlink_source(struct user_namespace *mnt_userns, * * Returns 0 if successful, -ve on error. */ -int may_linkat(struct user_namespace *mnt_userns, struct path *link) +int may_linkat(struct user_namespace *mnt_userns, const struct path *link) { struct inode *inode = link->dentry->d_inode; @@ -1472,8 +1474,7 @@ EXPORT_SYMBOL(follow_down); * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if * we meet a managed dentry that would need blocking. */ -static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, - struct inode **inode, unsigned *seqp) +static bool __follow_mount_rcu(struct nameidata *nd, struct path *path) { struct dentry *dentry = path->dentry; unsigned int flags = dentry->d_flags; @@ -1502,15 +1503,12 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, path->mnt = &mounted->mnt; dentry = path->dentry = mounted->mnt.mnt_root; nd->state |= ND_JUMPED; - *seqp = read_seqcount_begin(&dentry->d_seq); - *inode = dentry->d_inode; - /* - * We don't need to re-check ->d_seq after this - * ->d_inode read - there will be an RCU delay - * between mount hash removal and ->mnt_root - * becoming unpinned. - */ + nd->next_seq = read_seqcount_begin(&dentry->d_seq); flags = dentry->d_flags; + // makes sure that non-RCU pathwalk could reach + // this state. + if (read_seqretry(&mount_lock, nd->m_seq)) + return false; continue; } if (read_seqretry(&mount_lock, nd->m_seq)) @@ -1521,8 +1519,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, } static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, - struct path *path, struct inode **inode, - unsigned int *seqp) + struct path *path) { bool jumped; int ret; @@ -1530,16 +1527,15 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, path->mnt = nd->path.mnt; path->dentry = dentry; if (nd->flags & LOOKUP_RCU) { - unsigned int seq = *seqp; - if (unlikely(!*inode)) - return -ENOENT; - if (likely(__follow_mount_rcu(nd, path, inode, seqp))) + unsigned int seq = nd->next_seq; + if (likely(__follow_mount_rcu(nd, path))) return 0; - if (!try_to_unlazy_next(nd, dentry, seq)) - return -ECHILD; - // *path might've been clobbered by __follow_mount_rcu() + // *path and nd->next_seq might've been clobbered path->mnt = nd->path.mnt; path->dentry = dentry; + nd->next_seq = seq; + if (!try_to_unlazy_next(nd, dentry)) + return -ECHILD; } ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags); if (jumped) { @@ -1552,9 +1548,6 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, dput(path->dentry); if (path->mnt != nd->path.mnt) mntput(path->mnt); - } else { - *inode = d_backing_inode(path->dentry); - *seqp = 0; /* out of RCU mode, so the value doesn't matter */ } return ret; } @@ -1613,9 +1606,7 @@ static struct dentry *__lookup_hash(const struct qstr *name, return dentry; } -static struct dentry *lookup_fast(struct nameidata *nd, - struct inode **inode, - unsigned *seqp) +static struct dentry *lookup_fast(struct nameidata *nd) { struct dentry *dentry, *parent = nd->path.dentry; int status = 1; @@ -1626,8 +1617,7 @@ static struct dentry *lookup_fast(struct nameidata *nd, * going to fall back to non-racy lookup. */ if (nd->flags & LOOKUP_RCU) { - unsigned seq; - dentry = __d_lookup_rcu(parent, &nd->last, &seq); + dentry = __d_lookup_rcu(parent, &nd->last, &nd->next_seq); if (unlikely(!dentry)) { if (!try_to_unlazy(nd)) return ERR_PTR(-ECHILD); @@ -1635,28 +1625,16 @@ static struct dentry *lookup_fast(struct nameidata *nd, } /* - * This sequence count validates that the inode matches - * the dentry name information from lookup. - */ - *inode = d_backing_inode(dentry); - if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) - return ERR_PTR(-ECHILD); - - /* * This sequence count validates that the parent had no * changes while we did the lookup of the dentry above. - * - * The memory barrier in read_seqcount_begin of child is - * enough, we can use __read_seqcount_retry here. */ - if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq))) + if (read_seqcount_retry(&parent->d_seq, nd->seq)) return ERR_PTR(-ECHILD); - *seqp = seq; status = d_revalidate(dentry, nd->flags); if (likely(status > 0)) return dentry; - if (!try_to_unlazy_next(nd, dentry, seq)) + if (!try_to_unlazy_next(nd, dentry)) return ERR_PTR(-ECHILD); if (status == -ECHILD) /* we'd been told to redo it in non-rcu mode */ @@ -1737,7 +1715,7 @@ static inline int may_lookup(struct user_namespace *mnt_userns, return inode_permission(mnt_userns, nd->inode, MAY_EXEC); } -static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq) +static int reserve_stack(struct nameidata *nd, struct path *link) { if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) return -ELOOP; @@ -1752,9 +1730,9 @@ static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq) if (nd->flags & LOOKUP_RCU) { // we need to grab link before we do unlazy. And we can't skip // unlazy even if we fail to grab the link - cleanup needs it - bool grabbed_link = legitimize_path(nd, link, seq); + bool grabbed_link = legitimize_path(nd, link, nd->next_seq); - if (!try_to_unlazy(nd) != 0 || !grabbed_link) + if (!try_to_unlazy(nd) || !grabbed_link) return -ECHILD; if (nd_alloc_stack(nd)) @@ -1766,11 +1744,11 @@ static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq) enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4}; static const char *pick_link(struct nameidata *nd, struct path *link, - struct inode *inode, unsigned seq, int flags) + struct inode *inode, int flags) { struct saved *last; const char *res; - int error = reserve_stack(nd, link, seq); + int error = reserve_stack(nd, link); if (unlikely(error)) { if (!(nd->flags & LOOKUP_RCU)) @@ -1780,7 +1758,7 @@ static const char *pick_link(struct nameidata *nd, struct path *link, last = nd->stack + nd->depth++; last->link = *link; clear_delayed_call(&last->done); - last->seq = seq; + last->seq = nd->next_seq; if (flags & WALK_TRAILING) { error = may_follow_link(nd, inode); @@ -1842,43 +1820,50 @@ all_done: // pure jump * to do this check without having to look at inode->i_op, * so we keep a cache of "no, this doesn't need follow_link" * for the common case. + * + * NOTE: dentry must be what nd->next_seq had been sampled from. */ static const char *step_into(struct nameidata *nd, int flags, - struct dentry *dentry, struct inode *inode, unsigned seq) + struct dentry *dentry) { struct path path; - int err = handle_mounts(nd, dentry, &path, &inode, &seq); + struct inode *inode; + int err = handle_mounts(nd, dentry, &path); if (err < 0) return ERR_PTR(err); + inode = path.dentry->d_inode; if (likely(!d_is_symlink(path.dentry)) || ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) || (flags & WALK_NOFOLLOW)) { /* not a symlink or should not follow */ - if (!(nd->flags & LOOKUP_RCU)) { + if (nd->flags & LOOKUP_RCU) { + if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) + return ERR_PTR(-ECHILD); + if (unlikely(!inode)) + return ERR_PTR(-ENOENT); + } else { dput(nd->path.dentry); if (nd->path.mnt != path.mnt) mntput(nd->path.mnt); } nd->path = path; nd->inode = inode; - nd->seq = seq; + nd->seq = nd->next_seq; return NULL; } if (nd->flags & LOOKUP_RCU) { /* make sure that d_is_symlink above matches inode */ - if (read_seqcount_retry(&path.dentry->d_seq, seq)) + if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) return ERR_PTR(-ECHILD); } else { if (path.mnt == nd->path.mnt) mntget(path.mnt); } - return pick_link(nd, &path, inode, seq, flags); + return pick_link(nd, &path, inode, flags); } -static struct dentry *follow_dotdot_rcu(struct nameidata *nd, - struct inode **inodep, - unsigned *seqp) +static struct dentry *follow_dotdot_rcu(struct nameidata *nd) { struct dentry *parent, *old; @@ -1895,30 +1880,30 @@ static struct dentry *follow_dotdot_rcu(struct nameidata *nd, nd->path = path; nd->inode = path.dentry->d_inode; nd->seq = seq; - if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) + // makes sure that non-RCU pathwalk could reach this state + if (read_seqretry(&mount_lock, nd->m_seq)) return ERR_PTR(-ECHILD); /* we know that mountpoint was pinned */ } old = nd->path.dentry; parent = old->d_parent; - *inodep = parent->d_inode; - *seqp = read_seqcount_begin(&parent->d_seq); - if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq))) + nd->next_seq = read_seqcount_begin(&parent->d_seq); + // makes sure that non-RCU pathwalk could reach this state + if (read_seqcount_retry(&old->d_seq, nd->seq)) return ERR_PTR(-ECHILD); if (unlikely(!path_connected(nd->path.mnt, parent))) return ERR_PTR(-ECHILD); return parent; in_root: - if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) + if (read_seqretry(&mount_lock, nd->m_seq)) return ERR_PTR(-ECHILD); if (unlikely(nd->flags & LOOKUP_BENEATH)) return ERR_PTR(-ECHILD); - return NULL; + nd->next_seq = nd->seq; + return nd->path.dentry; } -static struct dentry *follow_dotdot(struct nameidata *nd, - struct inode **inodep, - unsigned *seqp) +static struct dentry *follow_dotdot(struct nameidata *nd) { struct dentry *parent; @@ -1942,15 +1927,12 @@ static struct dentry *follow_dotdot(struct nameidata *nd, dput(parent); return ERR_PTR(-ENOENT); } - *seqp = 0; - *inodep = parent->d_inode; return parent; in_root: if (unlikely(nd->flags & LOOKUP_BENEATH)) return ERR_PTR(-EXDEV); - dget(nd->path.dentry); - return NULL; + return dget(nd->path.dentry); } static const char *handle_dots(struct nameidata *nd, int type) @@ -1958,8 +1940,6 @@ static const char *handle_dots(struct nameidata *nd, int type) if (type == LAST_DOTDOT) { const char *error = NULL; struct dentry *parent; - struct inode *inode; - unsigned seq; if (!nd->root.mnt) { error = ERR_PTR(set_root(nd)); @@ -1967,17 +1947,12 @@ static const char *handle_dots(struct nameidata *nd, int type) return error; } if (nd->flags & LOOKUP_RCU) - parent = follow_dotdot_rcu(nd, &inode, &seq); + parent = follow_dotdot_rcu(nd); else - parent = follow_dotdot(nd, &inode, &seq); + parent = follow_dotdot(nd); if (IS_ERR(parent)) return ERR_CAST(parent); - if (unlikely(!parent)) - error = step_into(nd, WALK_NOFOLLOW, - nd->path.dentry, nd->inode, nd->seq); - else - error = step_into(nd, WALK_NOFOLLOW, - parent, inode, seq); + error = step_into(nd, WALK_NOFOLLOW, parent); if (unlikely(error)) return error; @@ -1989,9 +1964,9 @@ static const char *handle_dots(struct nameidata *nd, int type) * some fallback). */ smp_rmb(); - if (unlikely(__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq))) + if (__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq)) return ERR_PTR(-EAGAIN); - if (unlikely(__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq))) + if (__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)) return ERR_PTR(-EAGAIN); } } @@ -2001,8 +1976,6 @@ static const char *handle_dots(struct nameidata *nd, int type) static const char *walk_component(struct nameidata *nd, int flags) { struct dentry *dentry; - struct inode *inode; - unsigned seq; /* * "." and ".." are special - ".." especially so because it has * to be able to know about the current root directory and @@ -2013,7 +1986,7 @@ static const char *walk_component(struct nameidata *nd, int flags) put_link(nd); return handle_dots(nd, nd->last_type); } - dentry = lookup_fast(nd, &inode, &seq); + dentry = lookup_fast(nd); if (IS_ERR(dentry)) return ERR_CAST(dentry); if (unlikely(!dentry)) { @@ -2023,7 +1996,7 @@ static const char *walk_component(struct nameidata *nd, int flags) } if (!(flags & WALK_MORE) && nd->depth) put_link(nd); - return step_into(nd, flags, dentry, inode, seq); + return step_into(nd, flags, dentry); } /* @@ -2378,6 +2351,8 @@ static const char *path_init(struct nameidata *nd, unsigned flags) flags &= ~LOOKUP_RCU; if (flags & LOOKUP_RCU) rcu_read_lock(); + else + nd->seq = nd->next_seq = 0; nd->flags = flags; nd->state |= ND_JUMPED; @@ -2479,8 +2454,8 @@ static int handle_lookup_down(struct nameidata *nd) { if (!(nd->flags & LOOKUP_RCU)) dget(nd->path.dentry); - return PTR_ERR(step_into(nd, WALK_NOFOLLOW, - nd->path.dentry, nd->inode, nd->seq)); + nd->next_seq = nd->seq; + return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry)); } /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ @@ -2768,7 +2743,8 @@ struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name, EXPORT_SYMBOL(lookup_one); /** - * lookup_one_len_unlocked - filesystem helper to lookup single pathname component + * lookup_one_unlocked - filesystem helper to lookup single pathname component + * @mnt_userns: idmapping of the mount the lookup is performed from * @name: pathname component to lookup * @base: base directory to lookup from * @len: maximum length @len should be interpreted to @@ -2779,14 +2755,15 @@ EXPORT_SYMBOL(lookup_one); * Unlike lookup_one_len, it should be called without the parent * i_mutex held, and will take the i_mutex itself if necessary. */ -struct dentry *lookup_one_len_unlocked(const char *name, - struct dentry *base, int len) +struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns, + const char *name, struct dentry *base, + int len) { struct qstr this; int err; struct dentry *ret; - err = lookup_one_common(&init_user_ns, name, base, len, &this); + err = lookup_one_common(mnt_userns, name, base, len, &this); if (err) return ERR_PTR(err); @@ -2795,6 +2772,59 @@ struct dentry *lookup_one_len_unlocked(const char *name, ret = lookup_slow(&this, base, 0); return ret; } +EXPORT_SYMBOL(lookup_one_unlocked); + +/** + * lookup_one_positive_unlocked - filesystem helper to lookup single + * pathname component + * @mnt_userns: idmapping of the mount the lookup is performed from + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns + * known positive or ERR_PTR(). This is what most of the users want. + * + * Note that pinned negative with unlocked parent _can_ become positive at any + * time, so callers of lookup_one_unlocked() need to be very careful; pinned + * positives have >d_inode stable, so this one avoids such problems. + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * The helper should be called without i_mutex held. + */ +struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns, + const char *name, + struct dentry *base, int len) +{ + struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len); + + if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { + dput(ret); + ret = ERR_PTR(-ENOENT); + } + return ret; +} +EXPORT_SYMBOL(lookup_one_positive_unlocked); + +/** + * lookup_one_len_unlocked - filesystem helper to lookup single pathname component + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * Unlike lookup_one_len, it should be called without the parent + * i_mutex held, and will take the i_mutex itself if necessary. + */ +struct dentry *lookup_one_len_unlocked(const char *name, + struct dentry *base, int len) +{ + return lookup_one_unlocked(&init_user_ns, name, base, len); +} EXPORT_SYMBOL(lookup_one_len_unlocked); /* @@ -2808,12 +2838,7 @@ EXPORT_SYMBOL(lookup_one_len_unlocked); struct dentry *lookup_positive_unlocked(const char *name, struct dentry *base, int len) { - struct dentry *ret = lookup_one_len_unlocked(name, base, len); - if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { - dput(ret); - ret = ERR_PTR(-ENOENT); - } - return ret; + return lookup_one_positive_unlocked(&init_user_ns, name, base, len); } EXPORT_SYMBOL(lookup_positive_unlocked); @@ -2999,6 +3024,65 @@ void unlock_rename(struct dentry *p1, struct dentry *p2) EXPORT_SYMBOL(unlock_rename); /** + * mode_strip_umask - handle vfs umask stripping + * @dir: parent directory of the new inode + * @mode: mode of the new inode to be created in @dir + * + * Umask stripping depends on whether or not the filesystem supports POSIX + * ACLs. If the filesystem doesn't support it umask stripping is done directly + * in here. If the filesystem does support POSIX ACLs umask stripping is + * deferred until the filesystem calls posix_acl_create(). + * + * Returns: mode + */ +static inline umode_t mode_strip_umask(const struct inode *dir, umode_t mode) +{ + if (!IS_POSIXACL(dir)) + mode &= ~current_umask(); + return mode; +} + +/** + * vfs_prepare_mode - prepare the mode to be used for a new inode + * @mnt_userns: user namespace of the mount the inode was found from + * @dir: parent directory of the new inode + * @mode: mode of the new inode + * @mask_perms: allowed permission by the vfs + * @type: type of file to be created + * + * This helper consolidates and enforces vfs restrictions on the @mode of a new + * object to be created. + * + * Umask stripping depends on whether the filesystem supports POSIX ACLs (see + * the kernel documentation for mode_strip_umask()). Moving umask stripping + * after setgid stripping allows the same ordering for both non-POSIX ACL and + * POSIX ACL supporting filesystems. + * + * Note that it's currently valid for @type to be 0 if a directory is created. + * Filesystems raise that flag individually and we need to check whether each + * filesystem can deal with receiving S_IFDIR from the vfs before we enforce a + * non-zero type. + * + * Returns: mode to be passed to the filesystem + */ +static inline umode_t vfs_prepare_mode(struct user_namespace *mnt_userns, + const struct inode *dir, umode_t mode, + umode_t mask_perms, umode_t type) +{ + mode = mode_strip_sgid(mnt_userns, dir, mode); + mode = mode_strip_umask(dir, mode); + + /* + * Apply the vfs mandated allowed permission mask and set the type of + * file to be created before we call into the filesystem. + */ + mode &= (mask_perms & ~S_IFMT); + mode |= (type & S_IFMT); + + return mode; +} + +/** * vfs_create - create new file * @mnt_userns: user namespace of the mount the inode was found from * @dir: inode of @dentry @@ -3023,8 +3107,8 @@ int vfs_create(struct user_namespace *mnt_userns, struct inode *dir, if (!dir->i_op->create) return -EACCES; /* shouldn't it be ENOSYS? */ - mode &= S_IALLUGO; - mode |= S_IFREG; + + mode = vfs_prepare_mode(mnt_userns, dir, mode, S_IALLUGO, S_IFREG); error = security_inode_create(dir, dentry, mode); if (error) return error; @@ -3287,8 +3371,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file, if (open_flag & O_CREAT) { if (open_flag & O_EXCL) open_flag &= ~O_TRUNC; - if (!IS_POSIXACL(dir->d_inode)) - mode &= ~current_umask(); + mode = vfs_prepare_mode(mnt_userns, dir->d_inode, mode, mode, mode); if (likely(got_write)) create_error = may_o_create(mnt_userns, &nd->path, dentry, mode); @@ -3349,8 +3432,6 @@ static const char *open_last_lookups(struct nameidata *nd, struct dentry *dir = nd->path.dentry; int open_flag = op->open_flag; bool got_write = false; - unsigned seq; - struct inode *inode; struct dentry *dentry; const char *res; @@ -3366,7 +3447,7 @@ static const char *open_last_lookups(struct nameidata *nd, if (nd->last.name[nd->last.len]) nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; /* we _can_ be in RCU mode here */ - dentry = lookup_fast(nd, &inode, &seq); + dentry = lookup_fast(nd); if (IS_ERR(dentry)) return ERR_CAST(dentry); if (likely(dentry)) @@ -3420,7 +3501,7 @@ static const char *open_last_lookups(struct nameidata *nd, finish_lookup: if (nd->depth) put_link(nd); - res = step_into(nd, WALK_TRAILING, dentry, inode, seq); + res = step_into(nd, WALK_TRAILING, dentry); if (unlikely(res)) nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); return res; @@ -3521,6 +3602,7 @@ struct dentry *vfs_tmpfile(struct user_namespace *mnt_userns, child = d_alloc(dentry, &slash_name); if (unlikely(!child)) goto out_err; + mode = vfs_prepare_mode(mnt_userns, dir, mode, mode, mode); error = dir->i_op->tmpfile(mnt_userns, dir, child, mode); if (error) goto out_err; @@ -3673,18 +3755,14 @@ static struct dentry *filename_create(int dfd, struct filename *name, { struct dentry *dentry = ERR_PTR(-EEXIST); struct qstr last; + bool want_dir = lookup_flags & LOOKUP_DIRECTORY; + unsigned int reval_flag = lookup_flags & LOOKUP_REVAL; + unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL; int type; int err2; int error; - bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); - - /* - * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any - * other flags passed in are ignored! - */ - lookup_flags &= LOOKUP_REVAL; - error = filename_parentat(dfd, name, lookup_flags, path, &last, &type); + error = filename_parentat(dfd, name, reval_flag, path, &last, &type); if (error) return ERR_PTR(error); @@ -3698,11 +3776,13 @@ static struct dentry *filename_create(int dfd, struct filename *name, /* don't fail immediately if it's r/o, at least try to report other errors */ err2 = mnt_want_write(path->mnt); /* - * Do the final lookup. + * Do the final lookup. Suppress 'create' if there is a trailing + * '/', and a directory wasn't requested. */ - lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL; + if (last.name[last.len] && !want_dir) + create_flags = 0; inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); - dentry = __lookup_hash(&last, path->dentry, lookup_flags); + dentry = __lookup_hash(&last, path->dentry, reval_flag | create_flags); if (IS_ERR(dentry)) goto unlock; @@ -3716,7 +3796,7 @@ static struct dentry *filename_create(int dfd, struct filename *name, * all is fine. Let's be bastards - you had / on the end, you've * been asking for (non-existent) directory. -ENOENT for you. */ - if (unlikely(!is_dir && last.name[last.len])) { + if (unlikely(!create_flags)) { error = -ENOENT; goto fail; } @@ -3800,6 +3880,7 @@ int vfs_mknod(struct user_namespace *mnt_userns, struct inode *dir, if (!dir->i_op->mknod) return -EPERM; + mode = vfs_prepare_mode(mnt_userns, dir, mode, mode, mode); error = devcgroup_inode_mknod(mode, dev); if (error) return error; @@ -3850,9 +3931,8 @@ retry: if (IS_ERR(dentry)) goto out1; - if (!IS_POSIXACL(path.dentry->d_inode)) - mode &= ~current_umask(); - error = security_path_mknod(&path, dentry, mode, dev); + error = security_path_mknod(&path, dentry, + mode_strip_umask(path.dentry->d_inode, mode), dev); if (error) goto out2; @@ -3922,7 +4002,7 @@ int vfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir, if (!dir->i_op->mkdir) return -EPERM; - mode &= (S_IRWXUGO|S_ISVTX); + mode = vfs_prepare_mode(mnt_userns, dir, mode, S_IRWXUGO | S_ISVTX, 0); error = security_inode_mkdir(dir, dentry, mode); if (error) return error; @@ -3950,9 +4030,8 @@ retry: if (IS_ERR(dentry)) goto out_putname; - if (!IS_POSIXACL(path.dentry->d_inode)) - mode &= ~current_umask(); - error = security_path_mkdir(&path, dentry, mode); + error = security_path_mkdir(&path, dentry, + mode_strip_umask(path.dentry->d_inode, mode)); if (!error) { struct user_namespace *mnt_userns; mnt_userns = mnt_user_ns(path.mnt); @@ -5003,28 +5082,28 @@ int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) } EXPORT_SYMBOL(page_readlink); -/* - * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS - */ -int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) +int page_symlink(struct inode *inode, const char *symname, int len) { struct address_space *mapping = inode->i_mapping; + const struct address_space_operations *aops = mapping->a_ops; + bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS); struct page *page; void *fsdata; int err; - unsigned int flags = 0; - if (nofs) - flags |= AOP_FLAG_NOFS; + unsigned int flags; retry: - err = pagecache_write_begin(NULL, mapping, 0, len-1, - flags, &page, &fsdata); + if (nofs) + flags = memalloc_nofs_save(); + err = aops->write_begin(NULL, mapping, 0, len-1, &page, &fsdata); + if (nofs) + memalloc_nofs_restore(flags); if (err) goto fail; memcpy(page_address(page), symname, len-1); - err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, + err = aops->write_end(NULL, mapping, 0, len-1, len-1, page, fsdata); if (err < 0) goto fail; @@ -5036,13 +5115,6 @@ retry: fail: return err; } -EXPORT_SYMBOL(__page_symlink); - -int page_symlink(struct inode *inode, const char *symname, int len) -{ - return __page_symlink(inode, symname, len, - !mapping_gfp_constraint(inode->i_mapping, __GFP_FS)); -} EXPORT_SYMBOL(page_symlink); const struct inode_operations page_symlink_inode_operations = { |