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    Subject[PATCH 4.9 004/177] crypto: salsa20 - fix blkcipher_walk API usage
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Biggers <ebiggers@google.com>

    commit ecaaab5649781c5a0effdaf298a925063020500e upstream.

    When asked to encrypt or decrypt 0 bytes, both the generic and x86
    implementations of Salsa20 crash in blkcipher_walk_done(), either when
    doing 'kfree(walk->buffer)' or 'free_page((unsigned long)walk->page)',
    because walk->buffer and walk->page have not been initialized.

    The bug is that Salsa20 is calling blkcipher_walk_done() even when
    nothing is in 'walk.nbytes'. But blkcipher_walk_done() is only meant to
    be called when a nonzero number of bytes have been provided.

    The broken code is part of an optimization that tries to make only one
    call to salsa20_encrypt_bytes() to process inputs that are not evenly
    divisible by 64 bytes. To fix the bug, just remove this "optimization"
    and use the blkcipher_walk API the same way all the other users do.

    Reproducer:

    #include <linux/if_alg.h>
    #include <sys/socket.h>
    #include <unistd.h>

    int main()
    {
    int algfd, reqfd;
    struct sockaddr_alg addr = {
    .salg_type = "skcipher",
    .salg_name = "salsa20",
    };
    char key[16] = { 0 };

    algfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
    bind(algfd, (void *)&addr, sizeof(addr));
    reqfd = accept(algfd, 0, 0);
    setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key));
    read(reqfd, key, sizeof(key));
    }

    Reported-by: syzbot <syzkaller@googlegroups.com>
    Fixes: eb6f13eb9f81 ("[CRYPTO] salsa20_generic: Fix multi-page processing")
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/crypto/salsa20_glue.c | 7 -------
    crypto/salsa20_generic.c | 7 -------
    2 files changed, 14 deletions(-)

    --- a/arch/x86/crypto/salsa20_glue.c
    +++ b/arch/x86/crypto/salsa20_glue.c
    @@ -59,13 +59,6 @@ static int encrypt(struct blkcipher_desc

    salsa20_ivsetup(ctx, walk.iv);

    - if (likely(walk.nbytes == nbytes))
    - {
    - salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
    - walk.dst.virt.addr, nbytes);
    - return blkcipher_walk_done(desc, &walk, 0);
    - }
    -
    while (walk.nbytes >= 64) {
    salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
    walk.dst.virt.addr,
    --- a/crypto/salsa20_generic.c
    +++ b/crypto/salsa20_generic.c
    @@ -188,13 +188,6 @@ static int encrypt(struct blkcipher_desc

    salsa20_ivsetup(ctx, walk.iv);

    - if (likely(walk.nbytes == nbytes))
    - {
    - salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
    - walk.src.virt.addr, nbytes);
    - return blkcipher_walk_done(desc, &walk, 0);
    - }
    -
    while (walk.nbytes >= 64) {
    salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
    walk.src.virt.addr,

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