Crypto causes panic in scatterwalk_done with large/multiple buffers

[Jorgen Lundman <lundman@lundman.net>]

I have a situation where I setup scatterlists as:

 input scatterlist of 1, address ffffc90003627000 len 0x20000.

output scatterlist of 2, address 0 ffffc90002d45000 len 0x20000
                         address 1 ffff88003b079d98 len 0x000c

When I call crypto_aead_encrypt(req); it will die with:

kernel: [  925.151113] BUG: unable to handle kernel paging request at
ffffeb04000b5140
kernel: [  925.151253] IP: [<ffffffff812f4880>] scatterwalk_done+0x50/0x60
kernel: [  925.151325] PGD 0
kernel: [  925.151381] Oops: 0000 [#1] SMP
kernel: [  925.151442] CPU 1
kernel: [  925.154255]  [<ffffffff812f7640>] blkcipher_walk_done+0xb0/0x230
kernel: [  925.154255]  [<ffffffffa02e9169>] crypto_ctr_crypt+0x129/0x2b0 [ctr]
kernel: [  925.154255]  [<ffffffff812fe580>] ? crypto_aes_set_key+0x40/0x40
kernel: [  925.154255]  [<ffffffff812f6cbd>] async_encrypt+0x3d/0x40
kernel: [  925.154255]  [<ffffffffa0149326>] crypto_ccm_encrypt+0x246/0x290
[ccm]
kernel: [  925.154255]  [<ffffffffa01633bd>] crypto_encrypt+0x26d/0x2d0



What is interesting about that is, if I allocate a linear buffer instead:

  dst = kmalloc(cryptlen, GFP_KERNEL); // 0x20000 + 0x000c
  sg_init_table(sg, 1 );
  sg_set_buf(&sg[0], dst, cryptlen);

  crypto_aead_encrypt(req);

will no longer panic. However, when I try to copy the linear buffer back to
scatterlist;


  scatterwalk_map_and_copy(dst, sg, 0, cryptlen, 1);


then it will panic there instead.


However, if I replace it with the call:

    sg_copy_from_buffer(sg, sg_nents(sg),
                        dst, cryptlen);

everything works! <-

So, what am I doing wrong that makes scatterwalk_map_and_copy() fail, and
sg_copy_from_buffer() work fine? It would be nice if I could fix it, so I
did not need to copy to a temporary buffer.

Lund

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