From ba6cc29351b1fa0cb9adce91b88b9f3c3cbe9c46 Mon Sep 17 00:00:00 2001 From: Charalampos Mitrodimas Date: Sat, 16 Aug 2025 14:14:37 +0000 Subject: [PATCH] debugfs: fix mount options not being applied 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 Reviewed-by: Eric Sandeen Signed-off-by: Charalampos Mitrodimas Link: https://lore.kernel.org/r/20250816-debugfs-mount-opts-v3-1-d271dad57b5b@posteo.net Signed-off-by: Greg Kroah-Hartman --- fs/debugfs/inode.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index a0357b0cf362d..c12d649df6a54 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -183,6 +183,9 @@ static int debugfs_reconfigure(struct fs_context *fc) 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 super_block *sb, struct fs_context *fc) 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) -- 2.51.0