linux/fs/verity
Eric Biggers 0483913921 fsverity: reject FS_IOC_ENABLE_VERITY on mode 3 fds
Commit 56124d6c87 ("fsverity: support enabling with tree block size <
PAGE_SIZE") changed FS_IOC_ENABLE_VERITY to use __kernel_read() to read
the file's data, instead of direct pagecache accesses.

An unintended consequence of this is that the
'WARN_ON_ONCE(!(file->f_mode & FMODE_READ))' in __kernel_read() became
reachable by fuzz tests.  This happens if FS_IOC_ENABLE_VERITY is called
on a fd opened with access mode 3, which means "ioctl access only".

Arguably, FS_IOC_ENABLE_VERITY should work on ioctl-only fds.  But
ioctl-only fds are a weird Linux extension that is rarely used and that
few people even know about.  (The documentation for FS_IOC_ENABLE_VERITY
even specifically says it requires O_RDONLY.)  It's probably not
worthwhile to make the ioctl internally open a new fd just to handle
this case.  Thus, just reject the ioctl on such fds for now.

Fixes: 56124d6c87 ("fsverity: support enabling with tree block size < PAGE_SIZE")
Reported-by: syzbot+51177e4144d764827c45@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=2281afcbbfa8fdb92f9887479cc0e4180f1c6b28
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230406215106.235829-1-ebiggers@kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
2023-04-11 19:23:23 -07:00
..
enable.c fsverity: reject FS_IOC_ENABLE_VERITY on mode 3 fds 2023-04-11 19:23:23 -07:00
fsverity_private.h fsverity: support verification with tree block size < PAGE_SIZE 2023-01-09 19:06:03 -08:00
hash_algs.c fsverity: use WARN_ON_ONCE instead of WARN_ON 2023-04-11 19:23:15 -07:00
init.c fsverity: remove debug messages and CONFIG_FS_VERITY_DEBUG 2023-01-01 15:46:48 -08:00
Kconfig fsverity: remove debug messages and CONFIG_FS_VERITY_DEBUG 2023-01-01 15:46:48 -08:00
Makefile fs-verity: add FS_IOC_READ_VERITY_METADATA ioctl 2021-02-07 14:51:11 -08:00
measure.c fsverity: simplify fsverity_get_digest() 2022-11-29 21:07:41 -08:00
open.c fsverity: use WARN_ON_ONCE instead of WARN_ON 2023-04-11 19:23:15 -07:00
read_metadata.c fs-verity: use kmap_local_page() instead of kmap() 2022-08-19 15:19:55 -07:00
signature.c fs-verity: simplify sysctls with register_sysctl() 2023-03-27 21:17:02 -07:00
verify.c fsverity: Remove WQ_UNBOUND from fsverity read workqueue 2023-03-14 16:16:36 -07:00