Re: [LTP] [PATCH] ioctl_ficlone03: fix capabilities on immutable files

[Petr Vorel <pvorel@suse.cz>]

Hi all,

[ Cc Kent and other filesystem folks to be sure we don't hide a bug ]

> From: Andrea Cervesato <andrea.cervesato@suse.com>

> Make sure that capabilities requirements are satisfied when accessing
> immutable files. On OpenSUSE Tumbleweed 32bit bcachefs fails with the
> following error due to missing capabilities:

> tst_test.c:1833: TINFO: === Testing on bcachefs ===
> ..
> ioctl_ficlone03.c:74: TBROK: ioctl .. failed: ENOTTY (25)
> ioctl_ficlone03.c:89: TWARN: ioctl ..  failed: ENOTTY (25)
> ioctl_ficlone03.c:91: TWARN: ioctl ..  failed: ENOTTY (25)
> ioctl_ficlone03.c:98: TWARN: close(-1) failed: EBADF (9)

> Introduce CAP_LINUX_IMMUTABLE capability to make sure that test won't
> fail on other systems as well.

> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
>  testcases/kernel/syscalls/ioctl/ioctl_ficlone03.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

> diff --git a/testcases/kernel/syscalls/ioctl/ioctl_ficlone03.c b/testcases/kernel/syscalls/ioctl/ioctl_ficlone03.c
> index 6a9d270d9fb56f3a263f0aed976f62c4576e6a5f..6716423d9c96d9fc1d433f28e0ae1511b912ae2c 100644
> --- a/testcases/kernel/syscalls/ioctl/ioctl_ficlone03.c
> +++ b/testcases/kernel/syscalls/ioctl/ioctl_ficlone03.c
> @@ -122,5 +122,9 @@ static struct tst_test test = {
>  	.bufs = (struct tst_buffers []) {
>  		{&clone_range, .size = sizeof(struct file_clone_range)},
>  		{},
> -	}
> +	},
> +	.caps = (struct tst_cap []) {
> +		TST_CAP(TST_CAP_REQ, CAP_LINUX_IMMUTABLE),
> +		{}
> +	},

Reviewed-by: Petr Vorel <pvorel@suse.cz>

LGTM, obviously it is CAP_LINUX_IMMUTABLE related.

This looks like fs/bcachefs/fs-ioctl.c

static int bch2_inode_flags_set(struct btree_trans *trans,
				struct bch_inode_info *inode,
				struct bch_inode_unpacked *bi,
				void *p)
{
	...
	if (((newflags ^ oldflags) & (BCH_INODE_append|BCH_INODE_immutable)) &&
	    !capable(CAP_LINUX_IMMUTABLE))
		return -EPERM;


We don't test on vfat and exfat. If I try to do it fail the same way (bcachefs,
fat, exfat and ocfs2 use custom handler for FAT_IOCTL_SET_ATTRIBUTES).

I wonder why it does not fail for generic VFS fs/ioctl.c used by Btrfs and XFS:

/*
 * Generic function to check FS_IOC_FSSETXATTR/FS_IOC_SETFLAGS values and reject
 * any invalid configurations.
 *
 * Note: must be called with inode lock held.
 */
static int fileattr_set_prepare(struct inode *inode,
			      const struct fileattr *old_ma,
			      struct fileattr *fa)
{
	int err;

	/*
	 * The IMMUTABLE and APPEND_ONLY flags can only be changed by
	 * the relevant capability.
	 */
	if ((fa->flags ^ old_ma->flags) & (FS_APPEND_FL | FS_IMMUTABLE_FL) &&
	    !capable(CAP_LINUX_IMMUTABLE))
		return -EPERM;


Kind regards,
Petr

>  };

> ---
> base-commit: 753bd13472d4be44eb70ff183b007fe9c5fffa07
> change-id: 20250326-fix_ioctl_ficlone03_32bit_bcachefs-2ec15bd6c0c6

> Best regards,