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authorStefan Berger <stefanb@linux.ibm.com>2023-10-02 15:57:33 +0300
committerChristian Brauner <brauner@kernel.org>2023-11-18 16:54:07 +0300
commit8a924db2d7b5eb69ba08b1a0af46e9f1359a9bdf (patch)
treeb404e6c0538df7026450f53cad24ffd0fe22c193 /fs
parentb85ea95d086471afb4ad062012a4d73cd328fa86 (diff)
downloadlinux-8a924db2d7b5eb69ba08b1a0af46e9f1359a9bdf.tar.xz
fs: Pass AT_GETATTR_NOSEC flag to getattr interface function
When vfs_getattr_nosec() calls a filesystem's getattr interface function then the 'nosec' should propagate into this function so that vfs_getattr_nosec() can again be called from the filesystem's gettattr rather than vfs_getattr(). The latter would add unnecessary security checks that the initial vfs_getattr_nosec() call wanted to avoid. Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass with the new getattr_flags parameter to the getattr interface function. In overlayfs and ecryptfs use this flag to determine which one of the two functions to call. In a recent code change introduced to IMA vfs_getattr_nosec() ended up calling vfs_getattr() in overlayfs, which in turn called security_inode_getattr() on an exiting process that did not have current->fs set anymore, which then caused a kernel NULL pointer dereference. With this change the call to security_inode_getattr() can be avoided, thus avoiding the NULL pointer dereference. Reported-by: <syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com> Fixes: db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version") Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: <linux-fsdevel@vger.kernel.org> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Amir Goldstein <amir73il@gmail.com> Cc: Tyler Hicks <code@tyhicks.com> Cc: Mimi Zohar <zohar@linux.ibm.com> Suggested-by: Christian Brauner <brauner@kernel.org> Co-developed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> Link: https://lore.kernel.org/r/20231002125733.1251467-1-stefanb@linux.vnet.ibm.com Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/ecryptfs/inode.c12
-rw-r--r--fs/overlayfs/inode.c10
-rw-r--r--fs/overlayfs/overlayfs.h8
-rw-r--r--fs/stat.c6
4 files changed, 28 insertions, 8 deletions
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index a25dd3d20008..b0e8774c435a 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -998,6 +998,14 @@ static int ecryptfs_getattr_link(struct mnt_idmap *idmap,
return rc;
}
+static int ecryptfs_do_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int flags)
+{
+ if (flags & AT_GETATTR_NOSEC)
+ return vfs_getattr_nosec(path, stat, request_mask, flags);
+ return vfs_getattr(path, stat, request_mask, flags);
+}
+
static int ecryptfs_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int flags)
@@ -1006,8 +1014,8 @@ static int ecryptfs_getattr(struct mnt_idmap *idmap,
struct kstat lower_stat;
int rc;
- rc = vfs_getattr(ecryptfs_dentry_to_lower_path(dentry), &lower_stat,
- request_mask, flags);
+ rc = ecryptfs_do_getattr(ecryptfs_dentry_to_lower_path(dentry),
+ &lower_stat, request_mask, flags);
if (!rc) {
fsstack_copy_attr_all(d_inode(dentry),
ecryptfs_inode_to_lower(d_inode(dentry)));
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 345b8f161ca4..c63b31a460be 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -171,7 +171,7 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
type = ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
- err = vfs_getattr(&realpath, stat, request_mask, flags);
+ err = ovl_do_getattr(&realpath, stat, request_mask, flags);
if (err)
goto out;
@@ -196,8 +196,8 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
(!is_dir ? STATX_NLINK : 0);
ovl_path_lower(dentry, &realpath);
- err = vfs_getattr(&realpath, &lowerstat,
- lowermask, flags);
+ err = ovl_do_getattr(&realpath, &lowerstat, lowermask,
+ flags);
if (err)
goto out;
@@ -249,8 +249,8 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
ovl_path_lowerdata(dentry, &realpath);
if (realpath.dentry) {
- err = vfs_getattr(&realpath, &lowerdatastat,
- lowermask, flags);
+ err = ovl_do_getattr(&realpath, &lowerdatastat,
+ lowermask, flags);
if (err)
goto out;
} else {
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index ca88b2636a57..05c3dd597fa8 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -408,6 +408,14 @@ static inline bool ovl_open_flags_need_copy_up(int flags)
return ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC));
}
+static inline int ovl_do_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int flags)
+{
+ if (flags & AT_GETATTR_NOSEC)
+ return vfs_getattr_nosec(path, stat, request_mask, flags);
+ return vfs_getattr(path, stat, request_mask, flags);
+}
+
/* util.c */
int ovl_get_write_access(struct dentry *dentry);
void ovl_put_write_access(struct dentry *dentry);
diff --git a/fs/stat.c b/fs/stat.c
index 24bb0209e459..f721d26ec3f7 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -133,7 +133,8 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
idmap = mnt_idmap(path->mnt);
if (inode->i_op->getattr)
return inode->i_op->getattr(idmap, path, stat,
- request_mask, query_flags);
+ request_mask,
+ query_flags | AT_GETATTR_NOSEC);
generic_fillattr(idmap, request_mask, inode, stat);
return 0;
@@ -166,6 +167,9 @@ int vfs_getattr(const struct path *path, struct kstat *stat,
{
int retval;
+ if (WARN_ON_ONCE(query_flags & AT_GETATTR_NOSEC))
+ return -EPERM;
+
retval = security_inode_getattr(path);
if (retval)
return retval;