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Revision 64d107d3acca1565c39c044c459fd18f70943534 authored by Eric Biggers on 08 June 2017, 13:48:25 UTC, committed by James Morris on 09 June 2017, 03:29:47 UTC 
KEYS: encrypted: fix race causing incorrect HMAC calculations
 
The encrypted-keys module was using a single global HMAC transform,
which could be rekeyed by multiple threads concurrently operating on
different keys, causing incorrect HMAC values to be calculated.  Fix
this by allocating a new HMAC transform whenever we need to calculate a
HMAC.  Also simplify things a bit by allocating the shash_desc's using
SHASH_DESC_ON_STACK() for both the HMAC and unkeyed hashes.

The following script reproduces the bug:

    keyctl new_session
    keyctl add user master "abcdefghijklmnop" @s
    for i in $(seq 2); do
        (
            set -e
            for j in $(seq 1000); do
                keyid=$(keyctl add encrypted desc$i "new user:master 25" @s)
                datablob="$(keyctl pipe $keyid)"
                keyctl unlink $keyid > /dev/null
                keyid=$(keyctl add encrypted desc$i "load $datablob" @s)
                keyctl unlink $keyid > /dev/null
            done
        ) &
    done

Output with bug:

    [  439.691094] encrypted_key: bad hmac (-22)
    add_key: Invalid argument
    add_key: Invalid argument

Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
1 parent 794b4bc
Raw File
bounds.c 
/*
 * Generate definitions needed by the preprocessor.
 * This code generates raw asm output which is post-processed
 * to extract and format the required data.
 */

#define __GENERATING_BOUNDS_H
/* Include headers that define the enum constants of interest */
#include <linux/page-flags.h>
#include <linux/mmzone.h>
#include <linux/kbuild.h>
#include <linux/log2.h>
#include <linux/spinlock_types.h>

void foo(void)
{
	/* The enum constants to put into include/generated/bounds.h */
	DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
	DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES);
#ifdef CONFIG_SMP
	DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
#endif
	DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
	/* End of constants */
}
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