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[CRYPTO] blkcipher: Fix handling of kmalloc page straddling

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The function blkcipher_get_spot tries to return a buffer of
the specified length that does not straddle a page.  It has
an off-by-one bug so it may advance a page unnecessarily.

What's worse, one of its callers doesn't provide a buffer
that's sufficiently long for this operation.

This patch fixes both problems.  Thanks to Bob Gilligan for
diagnosing this problem and providing a fix.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Herbert Xu 2007-09-09 08:45:21 +01:00
parent b21010ed64
commit e4630f9fd8
1 changed files with 7 additions and 4 deletions
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11
crypto/blkcipher.c
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@ -59,11 +59,13 @@ static inline void blkcipher_unmap_dst(struct blkcipher_walk *walk)
scatterwalk_unmap(walk->dst.virt.addr, 1);
}
/* Get a spot of the specified length that does not straddle a page.
* The caller needs to ensure that there is enough space for this operation.
*/
static inline u8 *blkcipher_get_spot(u8 *start, unsigned int len)
{
if (offset_in_page(start + len) < len)
return (u8 *)((unsigned long)(start + len) & PAGE_MASK);
return start;
u8 *end_page = (u8 *)(((unsigned long)(start + len - 1)) & PAGE_MASK);
return start < end_page ? start : end_page;
}
static inline unsigned int blkcipher_done_slow(struct crypto_blkcipher *tfm,
@ -155,7 +157,8 @@ static inline int blkcipher_next_slow(struct blkcipher_desc *desc,
if (walk->buffer)
goto ok;
n = bsize * 2 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1));
n = bsize * 3 - (alignmask + 1) +
(alignmask & ~(crypto_tfm_ctx_alignment() - 1));
walk->buffer = kmalloc(n, GFP_ATOMIC);
if (!walk->buffer)
return blkcipher_walk_done(desc, walk, -ENOMEM);