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authorEric Biggers <ebiggers@google.com>2023-04-07 00:31:11 +0300
committerEric Biggers <ebiggers@google.com>2023-04-12 05:23:23 +0300
commit04839139213cf60d4c5fc792214a08830e294ff8 (patch)
tree8485c656890a7ee4ea4d4cbc170b893b024f9470 /block
parent39049b69ec9fc125fa1f314165dcc86f72cb72ec (diff)
downloadlinux-04839139213cf60d4c5fc792214a08830e294ff8.tar.xz
fsverity: reject FS_IOC_ENABLE_VERITY on mode 3 fds
Commit 56124d6c87fd ("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: 56124d6c87fd ("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>
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