Re: Kernel panic - encryption/decryption failed when open file on Arm64

[Herbert Xu]

On Mon, Sep 12, 2016 at 06:40:15PM +0100, Ard Biesheuvel wrote:
>
> So to me, it seems like we should be taking the blkcipher_next_slow()
> path, which does a kmalloc() and bails with -ENOMEM if that fails.

Indeed.  This was broken a long time ago.  It does seem to be
fixed in the new skcipher_walk code but here is a patch to fix
it for older kernels.

---8<---
Subject: crypto: skcipher - Fix blkcipher walk OOM crash

When we need to allocate a temporary blkcipher_walk_next and it
fails, the code is supposed to take the slow path of processing
the data block by block.  However, due to an unrelated change
we instead end up dereferencing the NULL pointer.

This patch fixes it by moving the unrelated bsize setting out
of the way so that we enter the slow path as inteded.

Fixes: 7607bd8ff03b ("[CRYPTO] blkcipher: Added blkcipher_walk_virt_block")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: xiakaixu <xiakaixu@xxxxxxxxxx>
Reported-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

diff --git a/crypto/blkcipher.c b/crypto/blkcipher.c
index 3699995..a832426 100644
--- a/crypto/blkcipher.c
+++ b/crypto/blkcipher.c
@@ -233,6 +233,8 @@ static int blkcipher_walk_next(struct blkcipher_desc *desc,
 		return blkcipher_walk_done(desc, walk, -EINVAL);
 	}
 
+	bsize = min(walk->walk_blocksize, n);
+
 	walk->flags &= ~(BLKCIPHER_WALK_SLOW | BLKCIPHER_WALK_COPY |
 			 BLKCIPHER_WALK_DIFF);
 	if (!scatterwalk_aligned(&walk->in, walk->alignmask) ||
@@ -245,7 +247,6 @@ static int blkcipher_walk_next(struct blkcipher_desc *desc,
 		}
 	}
 
-	bsize = min(walk->walk_blocksize, n);
 	n = scatterwalk_clamp(&walk->in, n);
 	n = scatterwalk_clamp(&walk->out, n);
 
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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