6.16-stable review patch. If anyone has any objections, please let me know.
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From: Charalampos Mitrodimas charmitro@posteo.net
commit ba6cc29351b1fa0cb9adce91b88b9f3c3cbe9c46 upstream.
Mount options (uid, gid, mode) are silently ignored when debugfs is mounted. This is a regression introduced during the conversion to the new mount API.
When the mount API conversion was done, the parsed options were never applied to the superblock when it was reused. As a result, the mount options were ignored when debugfs was mounted.
Fix this by following the same pattern as the tracefs fix in commit e4d32142d1de ("tracing: Fix tracefs mount options"). Call debugfs_reconfigure() in debugfs_get_tree() to apply the mount options to the superblock after it has been created or reused.
As an example, with the bug the "mode" mount option is ignored:
$ mount -o mode=0666 -t debugfs debugfs /tmp/debugfs_test $ mount | grep debugfs_test debugfs on /tmp/debugfs_test type debugfs (rw,relatime) $ ls -ld /tmp/debugfs_test drwx------ 25 root root 0 Aug 4 14:16 /tmp/debugfs_test
With the fix applied, it works as expected:
$ mount -o mode=0666 -t debugfs debugfs /tmp/debugfs_test $ mount | grep debugfs_test debugfs on /tmp/debugfs_test type debugfs (rw,relatime,mode=666) $ ls -ld /tmp/debugfs_test drw-rw-rw- 37 root root 0 Aug 2 17:28 /tmp/debugfs_test
Fixes: a20971c18752 ("vfs: Convert debugfs to use the new mount API") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220406 Cc: stable stable@kernel.org Reviewed-by: Eric Sandeen sandeen@redhat.com Signed-off-by: Charalampos Mitrodimas charmitro@posteo.net Link: https://lore.kernel.org/r/20250816-debugfs-mount-opts-v3-1-d271dad57b5b@post... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/debugfs/inode.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -183,6 +183,9 @@ static int debugfs_reconfigure(struct fs struct debugfs_fs_info *sb_opts = sb->s_fs_info; struct debugfs_fs_info *new_opts = fc->s_fs_info;
+ if (!new_opts) + return 0; + sync_filesystem(sb);
/* structure copy of new mount options to sb */ @@ -282,10 +285,16 @@ static int debugfs_fill_super(struct sup
static int debugfs_get_tree(struct fs_context *fc) { + int err; + if (!(debugfs_allow & DEBUGFS_ALLOW_API)) return -EPERM;
- return get_tree_single(fc, debugfs_fill_super); + err = get_tree_single(fc, debugfs_fill_super); + if (err) + return err; + + return debugfs_reconfigure(fc); }
static void debugfs_free_fc(struct fs_context *fc)