From: Eric Biggers <ebiggers@xxxxxxxxxx>
Commit 383203eff718 ("dh key: get rid of stack allocated array") changed
kdf_ctr() to assume that the length of key material to derive is a
multiple of the digest size. The length was supposed to be rounded up
accordingly. However, the round_up() macro was used which only gives
the correct result on power-of-2 arguments, whereas not all hash
algorithms have power-of-2 digest sizes. In some cases this resulted in
a write past the end of the 'outbuf' buffer.
Fix it by switching to roundup(), which works for non-power-of-2 inputs.
Reported-by: syzbot+486f97f892efeb2075a3@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+29d17b7898b41ee120a5@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+8a608baf8751184ec727@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+d04e58bd384f1fe0b112@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 383203eff718 ("dh key: get rid of stack allocated array")
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
security/keys/dh.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/security/keys/dh.c b/security/keys/dh.c
index f7403821db7f0..b203f7758f976 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -142,6 +142,8 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
* The src pointer is defined as Z || other info where Z is the shared secret
* from DH and other info is an arbitrary string (see SP800-56A section
* 5.8.1.2).
+ *
+ * 'dlen' must be a multiple of the digest size.
*/
static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
u8 *dst, unsigned int dlen, unsigned int zlen)
@@ -205,8 +207,8 @@ 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));
+ size_t outbuf_len = roundup(buflen,
+ crypto_shash_digestsize(sdesc->shash.tfm));
outbuf = kmalloc(outbuf_len, GFP_KERNEL);
if (!outbuf) {
--
2.17.1.1185.g55be947832-goog
