Messages in this thread Patch in this message | | | From | Brian Norris <> | Subject | [PATCH 1/2] debugfs: Only clobber mode/uid/gid on remount if asked | Date | Fri, 26 Aug 2022 17:44:16 -0700 |
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Users may have explicitly configured their debugfs permissions; we shouldn't overwrite those just because a second mount appeared.
Only clobber if the options were provided at mount time.
# Don't change /sys/kernel/debug/ permissions. mount -t debugfs none /mnt/foo
# Change /sys/kernel/debug/ mode and uid, but not gid. mount -t debugfs -o uid=bar,mode=0750 none /mnt/baz
Signed-off-by: Brian Norris <briannorris@chromium.org> --- I'm open to writing an LTP test case for this, if that seems like a good idea.
fs/debugfs/inode.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index 3dcf0b8b4e93..1e36ce013631 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -82,6 +82,8 @@ struct debugfs_mount_opts { kuid_t uid; kgid_t gid; umode_t mode; + /* Opt_* bitfield. */ + unsigned int opts; }; enum { @@ -111,6 +113,7 @@ static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts) kgid_t gid; char *p; + opts->opts = 0; opts->mode = DEBUGFS_DEFAULT_MODE; while ((p = strsep(&data, ",")) != NULL) { @@ -145,22 +148,34 @@ static int debugfs_parse_options(char *data, struct debugfs_mount_opts *opts) * but traditionally debugfs has ignored all mount options */ } + + opts->opts |= BIT(token); } return 0; } -static int debugfs_apply_options(struct super_block *sb) +static int debugfs_apply_options(struct super_block *sb, bool remount) { struct debugfs_fs_info *fsi = sb->s_fs_info; struct inode *inode = d_inode(sb->s_root); struct debugfs_mount_opts *opts = &fsi->mount_opts; - inode->i_mode &= ~S_IALLUGO; - inode->i_mode |= opts->mode; + /* + * On remount, only reset mode/uid/gid if they were provided as mount + * options. + */ + + if (!remount || opts->opts & BIT(Opt_mode)) { + inode->i_mode &= ~S_IALLUGO; + inode->i_mode |= opts->mode; + } + + if (!remount || opts->opts & BIT(Opt_uid)) + inode->i_uid = opts->uid; - inode->i_uid = opts->uid; - inode->i_gid = opts->gid; + if (!remount || opts->opts & BIT(Opt_gid)) + inode->i_gid = opts->gid; return 0; } @@ -175,7 +190,7 @@ static int debugfs_remount(struct super_block *sb, int *flags, char *data) if (err) goto fail; - debugfs_apply_options(sb); + debugfs_apply_options(sb, true); fail: return err; @@ -257,7 +272,7 @@ static int debug_fill_super(struct super_block *sb, void *data, int silent) sb->s_op = &debugfs_super_operations; sb->s_d_op = &debugfs_dops; - debugfs_apply_options(sb); + debugfs_apply_options(sb, false); return 0; -- 2.37.2.672.g94769d06f0-goog
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