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authorMiklos Szeredi <mszeredi@redhat.com>2016-10-01 08:32:32 +0300
committerMiklos Szeredi <mszeredi@redhat.com>2016-10-01 08:32:32 +0300
commita09f99eddef44035ec764075a37bace8181bec38 (patch)
treee232e770852cba1b8e339aebf9d6f37362304070 /fs/fuse
parent5e2b8828ff3d79aca8c3a1730652758753205b61 (diff)
downloadlinux-a09f99eddef44035ec764075a37bace8181bec38.tar.xz
fuse: fix killing s[ug]id in setattr
Fuse allowed VFS to set mode in setattr in order to clear suid/sgid on chown and truncate, and (since writeback_cache) write. The problem with this is that it'll potentially restore a stale mode. The poper fix would be to let the filesystems do the suid/sgid clearing on the relevant operations. Possibly some are already doing it but there's no way we can detect this. So fix this by refreshing and recalculating the mode. Do this only if ATTR_KILL_S[UG]ID is set to not destroy performance for writes. This is still racy but the size of the window is reduced. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Cc: <stable@vger.kernel.org>
Diffstat (limited to 'fs/fuse')
-rw-r--r--fs/fuse/dir.c32
1 files changed, 28 insertions, 4 deletions
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 3d3afa7ea57c..b7a690ed6a75 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1703,16 +1703,40 @@ error:
static int fuse_setattr(struct dentry *entry, struct iattr *attr)
{
struct inode *inode = d_inode(entry);
+ struct file *file = (attr->ia_valid & ATTR_FILE) ? attr->ia_file : NULL;
int ret;
if (!fuse_allow_current_process(get_fuse_conn(inode)))
return -EACCES;
- if (attr->ia_valid & ATTR_FILE)
- ret = fuse_do_setattr(inode, attr, attr->ia_file);
- else
- ret = fuse_do_setattr(inode, attr, NULL);
+ if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) {
+ int kill;
+
+ attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID |
+ ATTR_MODE);
+ /*
+ * ia_mode calculation may have used stale i_mode. Refresh and
+ * recalculate.
+ */
+ ret = fuse_do_getattr(inode, NULL, file);
+ if (ret)
+ return ret;
+
+ attr->ia_mode = inode->i_mode;
+ kill = should_remove_suid(entry);
+ if (kill & ATTR_KILL_SUID) {
+ attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode &= ~S_ISUID;
+ }
+ if (kill & ATTR_KILL_SGID) {
+ attr->ia_valid |= ATTR_MODE;
+ attr->ia_mode &= ~S_ISGID;
+ }
+ }
+ if (!attr->ia_valid)
+ return 0;
+ ret = fuse_do_setattr(inode, attr, file);
if (!ret) {
/* Directory mode changed, may need to revalidate access */
if (d_is_dir(entry) && (attr->ia_valid & ATTR_MODE))