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Date: Mon, 12 Mar 2018 22:29:07 -0600
From: Tycho Andersen <tycho@...ho.ws>
To: David Howells <dhowells@...hat.com>
Cc: keyrings@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
Tycho Andersen <tycho@...ho.ws>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>
Subject: [PATCH 2/2] dh key: get rid of stack array allocation
Similarly to the previous patch, we would like to get rid of stack
allocated arrays: https://lkml.org/lkml/2018/3/7/621
In this case, we can also use a malloc style approach to free the temporary
buffer, being careful to also use kzfree to free them (indeed, at least one
of these has a memzero_explicit, but it seems like maybe they both
should?).
Signed-off-by: Tycho Andersen <tycho@...ho.ws>
CC: David Howells <dhowells@...hat.com>
CC: James Morris <jmorris@...ei.org>
CC: "Serge E. Hallyn" <serge@...lyn.com>
---
security/keys/dh.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/security/keys/dh.c b/security/keys/dh.c
index d1ea9f325f94..f02261b24759 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -162,19 +162,27 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
goto err;
if (zlen && h) {
- u8 tmpbuffer[h];
+ u8 *tmpbuffer;
size_t chunk = min_t(size_t, zlen, h);
- memset(tmpbuffer, 0, chunk);
+
+ err = -ENOMEM;
+ tmpbuffer = kzalloc(chunk, GFP_KERNEL);
+ if (!tmpbuffer)
+ goto err;
do {
err = crypto_shash_update(desc, tmpbuffer,
chunk);
- if (err)
+ if (err) {
+ kzfree(tmpbuffer);
goto err;
+ }
zlen -= chunk;
chunk = min_t(size_t, zlen, h);
} while (zlen);
+
+ kzfree(tmpbuffer);
}
if (src && slen) {
@@ -184,13 +192,20 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
}
if (dlen < h) {
- u8 tmpbuffer[h];
+ u8 *tmpbuffer;
+
+ err = -ENOMEM;
+ tmpbuffer = kzalloc(h, GFP_KERNEL);
+ if (!tmpbuffer)
+ goto err;
err = crypto_shash_final(desc, tmpbuffer);
- if (err)
+ if (err) {
+ kzfree(tmpbuffer);
goto err;
+ }
memcpy(dst, tmpbuffer, dlen);
- memzero_explicit(tmpbuffer, h);
+ kzfree(tmpbuffer);
return 0;
} else {
err = crypto_shash_final(desc, dst);
--
2.15.1
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