Commit 3619dec5 authored by Eric Biggers's avatar Eric Biggers Committed by James Morris
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dh key: fix rounding up KDF output length

Commit 383203ef ("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.

Fixes: 383203ef

 ("dh key: get rid of stack allocated array")
Signed-off-by: default avatarEric Biggers <>
Acked-by: default avatarKees Cook <>
Acked-by: default avatarTycho Andersen <>
Signed-off-by: default avatarJames Morris <>
parent 2e20ce4a
......@@ -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
* '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,
size_t outbuf_len = roundup(buflen,
outbuf = kmalloc(outbuf_len, GFP_KERNEL);
if (!outbuf) {
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