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On sparc, if we have an alloca() like situation, as is the case with
SHASH_DESC_ON_STACK(), we can end up referencing deallocated stack
memory. The result can be that the value is clobbered if a trap
or interrupt arrives at just the right instruction.
It only occurs if the function ends returning a value from that
alloca() area and that value can be placed into the return value
register using a single instruction.
For example, in lib/libcrc32c.c:crc32c() we end up with a return
sequence like:
return %i7+8
lduw [%o5+16], %o0 ! MEM[(u32 *)__shash_desc.1_10 + 16B],
%o5 holds the base of the on-stack area allocated for the shash
descriptor. But the return released the stack frame and the
register window.
So if an intererupt arrives between 'return' and 'lduw', then
the value read at %o5+16 can be corrupted.
Add a data compiler barrier to work around this problem. This is
exactly what the gcc fix will end up doing as well, and it absolutely
should not change the code generated for other cpus (unless gcc
on them has the same bug :-)
With crucial insight from Eric Sandeen.
Cc: <stable@vger.kernel.org>
Reported-by: Anatoly Pugachev <matorola@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
81 lines
2.1 KiB
C
81 lines
2.1 KiB
C
/*
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* CRC32C
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*@Article{castagnoli-crc,
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* author = { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
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* title = {{Optimization of Cyclic Redundancy-Check Codes with 24
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* and 32 Parity Bits}},
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* journal = IEEE Transactions on Communication,
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* year = {1993},
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* volume = {41},
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* number = {6},
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* pages = {},
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* month = {June},
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*}
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* Used by the iSCSI driver, possibly others, and derived from the
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* the iscsi-crc.c module of the linux-iscsi driver at
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* http://linux-iscsi.sourceforge.net.
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*
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* Following the example of lib/crc32, this function is intended to be
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* flexible and useful for all users. Modules that currently have their
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* own crc32c, but hopefully may be able to use this one are:
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* net/sctp (please add all your doco to here if you change to
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* use this one!)
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* <endoflist>
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*
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* Copyright (c) 2004 Cisco Systems, Inc.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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*/
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#include <crypto/hash.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/crc32c.h>
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static struct crypto_shash *tfm;
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u32 crc32c(u32 crc, const void *address, unsigned int length)
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{
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SHASH_DESC_ON_STACK(shash, tfm);
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u32 ret, *ctx = (u32 *)shash_desc_ctx(shash);
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int err;
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shash->tfm = tfm;
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shash->flags = 0;
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*ctx = crc;
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err = crypto_shash_update(shash, address, length);
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BUG_ON(err);
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ret = *ctx;
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barrier_data(ctx);
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return ret;
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}
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EXPORT_SYMBOL(crc32c);
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static int __init libcrc32c_mod_init(void)
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{
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tfm = crypto_alloc_shash("crc32c", 0, 0);
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return PTR_ERR_OR_ZERO(tfm);
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}
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static void __exit libcrc32c_mod_fini(void)
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{
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crypto_free_shash(tfm);
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}
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module_init(libcrc32c_mod_init);
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module_exit(libcrc32c_mod_fini);
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MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
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MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations");
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MODULE_LICENSE("GPL");
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MODULE_SOFTDEP("pre: crc32c");
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