This is a note to let you know that I've just added the patch titled
crypto: dh - Fix double free of ctx->p
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: crypto-dh-fix-double-free-of-ctx-p.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 12d41a023efb01b846457ccdbbcbe2b65a87d530 Mon Sep 17 00:00:00 2001
From: Eric Biggers ebiggers@google.com Date: Sun, 5 Nov 2017 18:30:44 -0800 Subject: crypto: dh - Fix double free of ctx->p
From: Eric Biggers ebiggers@google.com
commit 12d41a023efb01b846457ccdbbcbe2b65a87d530 upstream.
When setting the secret with the software Diffie-Hellman implementation, if allocating 'g' failed (e.g. if it was longer than MAX_EXTERN_MPI_BITS), then 'p' was freed twice: once immediately, and once later when the crypto_kpp tfm was destroyed.
Fix it by using dh_free_ctx() (renamed to dh_clear_ctx()) in the error paths, as that correctly sets the pointers to NULL.
KASAN report:
MPI: mpi too large (32760 bits) ================================================================== BUG: KASAN: use-after-free in mpi_free+0x131/0x170 Read of size 4 at addr ffff88006c7cdf90 by task reproduce_doubl/367
CPU: 1 PID: 367 Comm: reproduce_doubl Not tainted 4.14.0-rc7-00040-g05298abde6fe #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: dump_stack+0xb3/0x10b ? mpi_free+0x131/0x170 print_address_description+0x79/0x2a0 ? mpi_free+0x131/0x170 kasan_report+0x236/0x340 ? akcipher_register_instance+0x90/0x90 __asan_report_load4_noabort+0x14/0x20 mpi_free+0x131/0x170 ? akcipher_register_instance+0x90/0x90 dh_exit_tfm+0x3d/0x140 crypto_kpp_exit_tfm+0x52/0x70 crypto_destroy_tfm+0xb3/0x250 __keyctl_dh_compute+0x640/0xe90 ? kasan_slab_free+0x12f/0x180 ? dh_data_from_key+0x240/0x240 ? key_create_or_update+0x1ee/0xb20 ? key_instantiate_and_link+0x440/0x440 ? lock_contended+0xee0/0xee0 ? kfree+0xcf/0x210 ? SyS_add_key+0x268/0x340 keyctl_dh_compute+0xb3/0xf1 ? __keyctl_dh_compute+0xe90/0xe90 ? SyS_add_key+0x26d/0x340 ? entry_SYSCALL_64_fastpath+0x5/0xbe ? trace_hardirqs_on_caller+0x3f4/0x560 SyS_keyctl+0x72/0x2c0 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x43ccf9 RSP: 002b:00007ffeeec96158 EFLAGS: 00000246 ORIG_RAX: 00000000000000fa RAX: ffffffffffffffda RBX: 000000000248b9b9 RCX: 000000000043ccf9 RDX: 00007ffeeec96170 RSI: 00007ffeeec96160 RDI: 0000000000000017 RBP: 0000000000000046 R08: 0000000000000000 R09: 0248b9b9143dc936 R10: 0000000000001000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000409670 R14: 0000000000409700 R15: 0000000000000000
Allocated by task 367: save_stack_trace+0x16/0x20 kasan_kmalloc+0xeb/0x180 kmem_cache_alloc_trace+0x114/0x300 mpi_alloc+0x4b/0x230 mpi_read_raw_data+0xbe/0x360 dh_set_secret+0x1dc/0x460 __keyctl_dh_compute+0x623/0xe90 keyctl_dh_compute+0xb3/0xf1 SyS_keyctl+0x72/0x2c0 entry_SYSCALL_64_fastpath+0x1f/0xbe
Freed by task 367: save_stack_trace+0x16/0x20 kasan_slab_free+0xab/0x180 kfree+0xb5/0x210 mpi_free+0xcb/0x170 dh_set_secret+0x2d7/0x460 __keyctl_dh_compute+0x623/0xe90 keyctl_dh_compute+0xb3/0xf1 SyS_keyctl+0x72/0x2c0 entry_SYSCALL_64_fastpath+0x1f/0xbe
Fixes: 802c7f1c84e4 ("crypto: dh - Add DH software implementation") Signed-off-by: Eric Biggers ebiggers@google.com Reviewed-by: Tudor Ambarus tudor.ambarus@microchip.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- crypto/dh.c | 33 +++++++++++++-------------------- 1 file changed, 13 insertions(+), 20 deletions(-)
--- a/crypto/dh.c +++ b/crypto/dh.c @@ -21,19 +21,12 @@ struct dh_ctx { MPI xa; };
-static inline void dh_clear_params(struct dh_ctx *ctx) +static void dh_clear_ctx(struct dh_ctx *ctx) { mpi_free(ctx->p); mpi_free(ctx->g); - ctx->p = NULL; - ctx->g = NULL; -} - -static void dh_free_ctx(struct dh_ctx *ctx) -{ - dh_clear_params(ctx); mpi_free(ctx->xa); - ctx->xa = NULL; + memset(ctx, 0, sizeof(*ctx)); }
/* @@ -71,10 +64,8 @@ static int dh_set_params(struct dh_ctx * return -EINVAL;
ctx->g = mpi_read_raw_data(params->g, params->g_size); - if (!ctx->g) { - mpi_free(ctx->p); + if (!ctx->g) return -EINVAL; - }
return 0; } @@ -86,21 +77,23 @@ static int dh_set_secret(struct crypto_k struct dh params;
/* Free the old MPI key if any */ - dh_free_ctx(ctx); + dh_clear_ctx(ctx);
if (crypto_dh_decode_key(buf, len, ¶ms) < 0) - return -EINVAL; + goto err_clear_ctx;
if (dh_set_params(ctx, ¶ms) < 0) - return -EINVAL; + goto err_clear_ctx;
ctx->xa = mpi_read_raw_data(params.key, params.key_size); - if (!ctx->xa) { - dh_clear_params(ctx); - return -EINVAL; - } + if (!ctx->xa) + goto err_clear_ctx;
return 0; + +err_clear_ctx: + dh_clear_ctx(ctx); + return -EINVAL; }
static int dh_compute_value(struct kpp_request *req) @@ -158,7 +151,7 @@ static void dh_exit_tfm(struct crypto_kp { struct dh_ctx *ctx = dh_get_ctx(tfm);
- dh_free_ctx(ctx); + dh_clear_ctx(ctx); }
static struct kpp_alg dh = {
Patches currently in stable-queue which might be from ebiggers@google.com are
queue-4.14/crypto-dh-don-t-permit-key-or-g-size-longer-than-p.patch queue-4.14/crypto-dh-don-t-permit-p-to-be-0.patch queue-4.14/crypto-dh-fix-double-free-of-ctx-p.patch