The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

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: [PATCH] crypto: dh - Fix double free of ctx->p

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") Cc: stable@vger.kernel.org # v4.8+ 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

diff --git a/crypto/dh.c b/crypto/dh.c index b1032a5c1bfa..aadaf36fb56f 100644 --- 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 *ctx, struct dh *params) 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_kpp *tfm, const void *buf, 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, &params) < 0) - return -EINVAL; + goto err_clear_ctx;

if (dh_set_params(ctx, &params) < 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_kpp *tfm) { struct dh_ctx *ctx = dh_get_ctx(tfm);

- dh_free_ctx(ctx); + dh_clear_ctx(ctx); }

static struct kpp_alg dh = {