Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
crypto: hash - Fix test underflow in shash_ahash_digest
The test on PAGE_SIZE - offset in shash_ahash_digest can underflow,
leading to execution of the fast path even if the data cannot be
mapped into a single page.
Fix this by splitting the test into four cases:
1) nbytes > sg->length: More than one SG entry, slow path.
2) !IS_ENABLED(CONFIG_HIGHMEM): fast path.
3) nbytes > (unsigned int)PAGE_SIZE - offset: Two highmem pages, slow path.
4) Highmem fast path.
Fixes: 5f7082ed4f48 ("crypto: hash - Export shash through hash")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
+26
-14
+26
-14
crypto/ahash.c
+26
-14
crypto/ahash.c
···
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#include <linux/cryptouser.h>
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#include <linux/err.h>
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#include <linux/kernel.h>
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+
#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
···
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unsigned int nbytes = req->nbytes;
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struct scatterlist *sg;
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unsigned int offset;
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struct page *page;
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const u8 *data;
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int err;
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-
if (ahash_request_isvirt(req))
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return crypto_shash_digest(desc, req->svirt, nbytes,
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req->result);
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data = req->svirt;
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if (!nbytes || ahash_request_isvirt(req))
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return crypto_shash_digest(desc, data, nbytes, req->result);
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-
if (nbytes &&
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(sg = req->src, offset = sg->offset,
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nbytes <= min(sg->length, ((unsigned int)(PAGE_SIZE)) - offset))) {
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void *data;
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sg = req->src;
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if (nbytes > sg->length)
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return crypto_shash_init(desc) ?:
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shash_ahash_finup(req, desc);
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-
data = kmap_local_page(sg_page(sg));
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err = crypto_shash_digest(desc, data + offset, nbytes,
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req->result);
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kunmap_local(data);
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} else
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err = crypto_shash_init(desc) ?:
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shash_ahash_finup(req, desc);
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page = sg_page(sg);
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offset = sg->offset;
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data = lowmem_page_address(page) + offset;
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if (!IS_ENABLED(CONFIG_HIGHMEM))
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return crypto_shash_digest(desc, data, nbytes, req->result);
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page += offset >> PAGE_SHIFT;
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offset = offset_in_page(offset);
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+
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if (nbytes > (unsigned int)PAGE_SIZE - offset)
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return crypto_shash_init(desc) ?:
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shash_ahash_finup(req, desc);
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+
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data = kmap_local_page(page);
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err = crypto_shash_digest(desc, data + offset, nbytes,
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req->result);
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kunmap_local(data);
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return err;
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}
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EXPORT_SYMBOL_GPL(shash_ahash_digest);