On 9 September 2016 at 11:19, xiakaixu <xiakaixu@xxxxxxxxxx> wrote:
> Hi,
>
> After a deeply research about this crash, seems it is a specific
> bug that only exists in armv8 board. And it occurs in this function
> in arch/arm64/crypto/aes-glue.c.
>
> static int ctr_encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
> struct scatterlist *src, unsigned int nbytes)
> {
> ...
>
> desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
> blkcipher_walk_init(&walk, dst, src, nbytes);
> err = blkcipher_walk_virt_block(desc, &walk, AES_BLOCK_SIZE); --->
> page allocation failed
>
> ...
>
> while ((blocks = (walk.nbytes / AES_BLOCK_SIZE))) { ---->
> walk.nbytes = 0, and skip this loop
> aes_ctr_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
> (u8 *)ctx->key_enc, rounds, blocks, walk.iv,
> first);
> ...
> err = blkcipher_walk_done(desc, &walk,
> walk.nbytes % AES_BLOCK_SIZE);
> }
> if (nbytes) { ---->
> enter this if() statement
> u8 *tdst = walk.dst.virt.addr + blocks * AES_BLOCK_SIZE;
> u8 *tsrc = walk.src.virt.addr + blocks * AES_BLOCK_SIZE;
> ...
>
> aes_ctr_encrypt(tail, tsrc, (u8 *)ctx->key_enc, rounds,
> ----> the the sencond input parameter is NULL, so crash...
> blocks, walk.iv, first);
> ...
> }
> ...
> }
>
>
> If the page allocation failed in the function blkcipher_walk_virt_block(),
> the variable walk.nbytes = 0, so it will skip the while() loop and enter
> the if(nbytes) statment. But here the varibale tsrc is NULL and it is also
> the sencond input parameter of the function aes_ctr_encrypt()... Kernel
> Panic...
>
> I have also researched the similar function in other architectures, and
> there if(walk.nbytes) is used, not this if(nbytes) statement in the armv8.
> so I think this armv8 function ctr_encrypt() should deal with the page
> allocation failed situation.
>
OK, thanks for the report, and for the analysis. I will investigate,
and propose a fix
Thanks,
Ard.
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