dm-verity: recheck the hash after a failure

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commit 9177f3c0de upstream.

If a userspace process reads (with O_DIRECT) multiple blocks into the same
buffer, dm-verity reports an error [1].

This commit fixes dm-verity, so that if hash verification fails, the data
is read again into a kernel buffer (where userspace can't modify it) and
the hash is rechecked. If the recheck succeeds, the content of the kernel
buffer is copied into the user buffer; if the recheck fails, an error is
reported.

[1] https://people.redhat.com/~mpatocka/testcases/blk-auth-modify/read2.c

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Mikulas Patocka 2024-02-19 21:28:09 +01:00 • committed by Greg Kroah-Hartman

parent e08c2a8d27

commit 27c1ade606

2 changed files with 86 additions and 6 deletions

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86

drivers/md/dm-verity-target.c

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6

drivers/md/dm-verity.h

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