diff options
| author | Tycho Andersen <tycho@tycho.ws> | 2018-04-24 22:26:38 +0200 |
|---|---|---|
| committer | James Morris <james.morris@microsoft.com> | 2018-05-11 22:07:47 +0200 |
| commit | 383203eff718d7397ffc68ac6c3ed644d3017fc7 (patch) | |
| tree | 2218547fb400fa5b4425ec29fddfea65d95c0d96 /security/keys/dh.c | |
| parent | big key: get rid of stack array allocation (diff) | |
| download | linux-383203eff718d7397ffc68ac6c3ed644d3017fc7.tar.xz linux-383203eff718d7397ffc68ac6c3ed644d3017fc7.zip | |
dh key: get rid of stack allocated array
We're interested in getting rid of all of the stack allocated arrays in the
kernel: https://lkml.org/lkml/2018/3/7/621
This particular vla is used as a temporary output buffer in case there is
too much hash output for the destination buffer. Instead, let's just
allocate a buffer that's big enough initially, but only copy back to
userspace the amount that was originally asked for.
v2: allocate enough in the original output buffer vs creating a temporary
output buffer
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Reviewed-by: Kees Cook <keescook@chromium.org>
CC: David Howells <dhowells@redhat.com>
CC: James Morris <jmorris@namei.org>
CC: "Serge E. Hallyn" <serge@hallyn.com>
CC: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
Diffstat (limited to 'security/keys/dh.c')
| -rw-r--r-- | security/keys/dh.c | 29 |
1 files changed, 10 insertions, 19 deletions
diff --git a/security/keys/dh.c b/security/keys/dh.c index d1ea9f325f94..9fecaea6c298 100644 --- a/security/keys/dh.c +++ b/security/keys/dh.c @@ -183,24 +183,13 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen, goto err; } - if (dlen < h) { - u8 tmpbuffer[h]; - - err = crypto_shash_final(desc, tmpbuffer); - if (err) - goto err; - memcpy(dst, tmpbuffer, dlen); - memzero_explicit(tmpbuffer, h); - return 0; - } else { - err = crypto_shash_final(desc, dst); - if (err) - goto err; + err = crypto_shash_final(desc, dst); + if (err) + goto err; - dlen -= h; - dst += h; - counter = cpu_to_be32(be32_to_cpu(counter) + 1); - } + dlen -= h; + dst += h; + counter = cpu_to_be32(be32_to_cpu(counter) + 1); } return 0; @@ -216,14 +205,16 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc, { uint8_t *outbuf = NULL; int ret; + size_t outbuf_len = round_up(buflen, + crypto_shash_digestsize(sdesc->shash.tfm)); - outbuf = kmalloc(buflen, GFP_KERNEL); + outbuf = kmalloc(outbuf_len, GFP_KERNEL); if (!outbuf) { ret = -ENOMEM; goto err; } - ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, buflen, lzero); + ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero); if (ret) goto err; |