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authorMikulas Patocka <mpatocka@redhat.com>2014-09-11 13:43:12 -0400
committerWilly Tarreau <w@1wt.eu>2014-11-23 10:55:45 +0100
commit0cfd94f0456b86f937cb3b54aa842cda8ecd6bac (patch)
tree8e0326426456507c2864494e10ccdb99374ad752 /drivers
parent5e4b587d654fc122803dbe1d4d718d9ca59c198b (diff)
dm crypt: fix access beyond the end of allocated space
commit d49ec52ff6ddcda178fc2476a109cf1bd1fa19ed upstream The DM crypt target accesses memory beyond allocated space resulting in a crash on 32 bit x86 systems. This bug is very old (it dates back to 2.6.25 commit 3a7f6c990ad04 "dm crypt: use async crypto"). However, this bug was masked by the fact that kmalloc rounds the size up to the next power of two. This bug wasn't exposed until 3.17-rc1 commit 298a9fa08a ("dm crypt: use per-bio data"). By switching to using per-bio data there was no longer any padding beyond the end of a dm-crypt allocated memory block. To minimize allocation overhead dm-crypt puts several structures into one block allocated with kmalloc. The block holds struct ablkcipher_request, cipher-specific scratch pad (crypto_ablkcipher_reqsize(any_tfm(cc))), struct dm_crypt_request and an initialization vector. The variable dmreq_start is set to offset of struct dm_crypt_request within this memory block. dm-crypt allocates the block with this size: cc->dmreq_start + sizeof(struct dm_crypt_request) + cc->iv_size. When accessing the initialization vector, dm-crypt uses the function iv_of_dmreq, which performs this calculation: ALIGN((unsigned long)(dmreq + 1), crypto_ablkcipher_alignmask(any_tfm(cc)) + 1). dm-crypt allocated "cc->iv_size" bytes beyond the end of dm_crypt_request structure. However, when dm-crypt accesses the initialization vector, it takes a pointer to the end of dm_crypt_request, aligns it, and then uses it as the initialization vector. If the end of dm_crypt_request is not aligned on a crypto_ablkcipher_alignmask(any_tfm(cc)) boundary the alignment causes the initialization vector to point beyond the allocated space. Fix this bug by calculating the variable iv_size_padding and adding it to the allocated size. Also correct the alignment of dm_crypt_request. struct dm_crypt_request is specific to dm-crypt (it isn't used by the crypto subsystem at all), so it is aligned on __alignof__(struct dm_crypt_request). Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> [wt: minor context adaptations, hopefully ok] Signed-off-by: Willy Tarreau <w@1wt.eu>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/md/dm-crypt.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 959d6d14cee0..a44a9081b0bc 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -998,6 +998,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
char *ivopts;
unsigned int key_size;
unsigned long long tmpll;
+ size_t iv_size_padding;
if (argc != 5) {
ti->error = "Not enough arguments";
@@ -1106,12 +1107,23 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
cc->dmreq_start = sizeof(struct ablkcipher_request);
cc->dmreq_start += crypto_ablkcipher_reqsize(tfm);
- cc->dmreq_start = ALIGN(cc->dmreq_start, crypto_tfm_ctx_alignment());
- cc->dmreq_start += crypto_ablkcipher_alignmask(tfm) &
- ~(crypto_tfm_ctx_alignment() - 1);
+ cc->dmreq_start = ALIGN(cc->dmreq_start, __alignof__(struct dm_crypt_request));
+
+ if (crypto_ablkcipher_alignmask(tfm) < CRYPTO_MINALIGN) {
+ /* Allocate the padding exactly */
+ iv_size_padding = -(cc->dmreq_start + sizeof(struct dm_crypt_request))
+ & crypto_ablkcipher_alignmask(tfm);
+ } else {
+ /*
+ * If the cipher requires greater alignment than kmalloc
+ * alignment, we don't know the exact position of the
+ * initialization vector. We must assume worst case.
+ */
+ iv_size_padding = crypto_ablkcipher_alignmask(tfm);
+ }
cc->req_pool = mempool_create_kmalloc_pool(MIN_IOS, cc->dmreq_start +
- sizeof(struct dm_crypt_request) + cc->iv_size);
+ sizeof(struct dm_crypt_request) + iv_size_padding + cc->iv_size);
if (!cc->req_pool) {
ti->error = "Cannot allocate crypt request mempool";
goto bad_req_pool;