On Wed, Feb 1, 2017 at 7:45 PM, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> wrote:
> On Tue, Jan 31, 2017 at 02:16:31PM +0100, Dmitry Vyukov wrote:
>> Hello,
>>
>> I am getting the following reports with low frequency while running
>> syzkaller fuzzer. Unfortunately they are not reproducible and happen
>> in a background thread, so it is difficult to extract any context on
>> my side. I see only few such crashes per week, so most likely it is
>> some hard to trigger data race. The following reports are from mmotm
>> tree, commits 00e20cfc2bf04a0cbe1f5405f61c8426f43eee84 and
>> fff7e71eac7788904753136f09bcad7471f7799e. Any ideas as to how this can
>> happen?
>>
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000060
>> IP: [<ffffffff813fc09e>] sha512_mb_mgr_get_comp_job_avx2+0x6e/0xee
>> arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S:251
>> PGD 1d2395067 [ 220.874864] PUD 1d2860067
>> Oops: 0002 [#1] SMP KASAN
>> Dumping ftrace buffer:
>> (ftrace buffer empty)
>> Modules linked in:
>> CPU: 0 PID: 516 Comm: kworker/0:1 Not tainted 4.9.0 #4
>> Hardware name: Google Google Compute Engine/Google Compute Engine,
>> BIOS Google 01/01/2011
>> Workqueue: crypto mcryptd_queue_worker
>> task: ffff8801d9f346c0 task.stack: ffff8801d9f08000
>> RIP: 0010:[<ffffffff813fc09e>] [<ffffffff813fc09e>]
>> sha512_mb_mgr_get_comp_job_avx2+0x6e/0xee
>> arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S:251
>> RSP: 0018:ffff8801d9f0eef8 EFLAGS: 00010202
>> RAX: 0000000000000000 RBX: ffff8801d7db1190 RCX: 0000000000000006
>> RDX: 0000000000000001 RSI: ffff8801d9f34ee8 RDI: ffff8801d7db1040
>> RBP: ffff8801d9f0f258 R08: 0000000100000000 R09: 0000000000000001
>> R10: 0000000000000002 R11: 0000000000000003 R12: ffff8801d9f0f230
>> R13: ffff8801c8bbc4e0 R14: ffff8801c8bbc530 R15: ffff8801d9f0ef70
>> FS: 0000000000000000(0000) GS:ffff8801dc000000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000060 CR3: 00000001cc15a000 CR4: 00000000001406f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Stack:
>> ffff8801d7db1040 ffffffff813fa207 dffffc0000000000 ffffe8ffffc0f238
>> 0000000000000002 1ffff1003b3e1dea ffffe8ffffc0f218 ffff8801d9f0f190
>> 0000000000000282 ffffe8ffffc0f140 ffffe8ffffc0f220 0000000041b58ab3
>> Call Trace:
>> [<ffffffff813fb407>] sha512_mb_update+0x2f7/0x4e0
>> arch/x86/crypto/sha512-mb/sha512_mb.c:588
>> [<ffffffff8219d4ad>] crypto_ahash_update include/crypto/hash.h:512 [inline]
>> [<ffffffff8219d4ad>] ahash_mcryptd_update crypto/mcryptd.c:627 [inline]
>> [<ffffffff8219d4ad>] mcryptd_hash_update+0xcd/0x1c0 crypto/mcryptd.c:373
>> [<ffffffff8219c99f>] mcryptd_queue_worker+0xff/0x6a0 crypto/mcryptd.c:181
>> [<ffffffff81492960>] process_one_work+0xbd0/0x1c10 kernel/workqueue.c:2096
>> [<ffffffff81493bc3>] worker_thread+0x223/0x1990 kernel/workqueue.c:2230
>> [<ffffffff814abb33>] kthread+0x323/0x3e0 kernel/kthread.c:209
>> [<ffffffff8436fbaa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
>> Code: 49 0f 42 d3 48 f7 c2 f0 ff ff ff 0f 85 9a 00 00 00 48 83 e2 0f
>> 48 6b da 08 48 8d 9c 1f 48 01 00 00 48 8b 03 48 c7 03 00 00 00 00 <c7>
>> 40 60 02 00 00 00 48 8b 9f 40 01 00 00 48 c1 e3 08 48 09 d3
>> RIP [<ffffffff813fc09e>] sha512_mb_mgr_get_comp_job_avx2+0x6e/0xee
>> arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S:251
>> RSP <ffff8801d9f0eef8>
>> CR2: 0000000000000060
>> ---[ end trace 139fd4cda5dfe2c4 ]---
>>
>
> Dmitry,
>
> One theory that Mehga and I have is that perhaps the flusher
> and regular computaion updates are stepping on each other.
> Can you try this patch and see if it helps?
No, for this one I can't. Sorry.
It happens with very low frequency and only one fuzzer that tests
mmotm tree. If/when this is committed, I can keep an eye on these
reports and notify if I still see them.
If you have a hypothesis as to how it happens, perhaps you could write
a test that provokes the crash and maybe add some sleeps to kernel
code or alter timeouts to increase probability.
> --->8---
>
> From: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Subject: [PATCH] crypto/sha512-mb: Protect sha512 mb ctx mgr access
> To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>, Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, David Miller <davem@xxxxxxxxxxxxx>, linux-crypto@xxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>, megha.dey@xxxxxxxxxxxxxxx, fenghua.yu@xxxxxxxxx
>
> The flusher and regular multi-buffer computation via mcryptd may race with another.
> Add here a lock and turn off interrupt to to access multi-buffer
> computation state cstate->mgr before a round of computation. This should
> prevent the flusher code jumping in.
>
> Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> ---
> arch/x86/crypto/sha512-mb/sha512_mb.c | 64 +++++++++++++++++++++++------------
> 1 file changed, 42 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/crypto/sha512-mb/sha512_mb.c b/arch/x86/crypto/sha512-mb/sha512_mb.c
> index d210174..f3c1c21 100644
> --- a/arch/x86/crypto/sha512-mb/sha512_mb.c
> +++ b/arch/x86/crypto/sha512-mb/sha512_mb.c
> @@ -221,7 +221,7 @@ static struct sha512_hash_ctx *sha512_ctx_mgr_resubmit
> }
>
> static struct sha512_hash_ctx
> - *sha512_ctx_mgr_get_comp_ctx(struct sha512_ctx_mgr *mgr)
> + *sha512_ctx_mgr_get_comp_ctx(struct mcryptd_alg_cstate *cstate)
> {
> /*
> * If get_comp_job returns NULL, there are no jobs complete.
> @@ -233,11 +233,17 @@ static struct sha512_hash_ctx
> * Otherwise, all jobs currently being managed by the hash_ctx_mgr
> * still need processing.
> */
> + struct sha512_ctx_mgr *mgr;
> struct sha512_hash_ctx *ctx;
> + unsigned long flags;
>
> + mgr = cstate->mgr;
> + spin_lock_irqsave(&cstate->work_lock, flags);
> ctx = (struct sha512_hash_ctx *)
> sha512_job_mgr_get_comp_job(&mgr->mgr);
> - return sha512_ctx_mgr_resubmit(mgr, ctx);
> + ctx = sha512_ctx_mgr_resubmit(mgr, ctx);
> + spin_unlock_irqrestore(&cstate->work_lock, flags);
> + return ctx;
> }
>
> static void sha512_ctx_mgr_init(struct sha512_ctx_mgr *mgr)
> @@ -246,12 +252,17 @@ static void sha512_ctx_mgr_init(struct sha512_ctx_mgr *mgr)
> }
>
> static struct sha512_hash_ctx
> - *sha512_ctx_mgr_submit(struct sha512_ctx_mgr *mgr,
> + *sha512_ctx_mgr_submit(struct mcryptd_alg_cstate *cstate,
> struct sha512_hash_ctx *ctx,
> const void *buffer,
> uint32_t len,
> int flags)
> {
> + struct sha512_ctx_mgr *mgr;
> + unsigned long irqflags;
> +
> + mgr = cstate->mgr;
> + spin_lock_irqsave(&cstate->work_lock, irqflags);
> if (flags & (~HASH_ENTIRE)) {
> /*
> * User should not pass anything other than FIRST, UPDATE, or
> @@ -351,20 +362,26 @@ static struct sha512_hash_ctx
> }
> }
>
> - return sha512_ctx_mgr_resubmit(mgr, ctx);
> + ctx = sha512_ctx_mgr_resubmit(mgr, ctx);
> + spin_unlock_irqrestore(&cstate->work_lock, irqflags);
> + return ctx;
> }
>
> -static struct sha512_hash_ctx *sha512_ctx_mgr_flush(struct sha512_ctx_mgr *mgr)
> +static struct sha512_hash_ctx *sha512_ctx_mgr_flush(struct mcryptd_alg_cstate *cstate)
> {
> + struct sha512_ctx_mgr *mgr;
> struct sha512_hash_ctx *ctx;
> + unsigned long flags;
>
> + mgr = cstate->mgr;
> + spin_lock_irqsave(&cstate->work_lock, flags);
> while (1) {
> ctx = (struct sha512_hash_ctx *)
> sha512_job_mgr_flush(&mgr->mgr);
>
> /* If flush returned 0, there are no more jobs in flight. */
> if (!ctx)
> - return NULL;
> + break;
>
> /*
> * If flush returned a job, resubmit the job to finish
> @@ -378,8 +395,10 @@ static struct sha512_hash_ctx *sha512_ctx_mgr_flush(struct sha512_ctx_mgr *mgr)
> * the sha512_ctx_mgr still need processing. Loop.
> */
> if (ctx)
> - return ctx;
> + break;
> }
> + spin_unlock_irqrestore(&cstate->work_lock, flags);
> + return ctx;
> }
>
> static int sha512_mb_init(struct ahash_request *areq)
> @@ -439,11 +458,11 @@ static int sha_finish_walk(struct mcryptd_hash_request_ctx **ret_rctx,
> sha_ctx = (struct sha512_hash_ctx *)
> ahash_request_ctx(&rctx->areq);
> kernel_fpu_begin();
> - sha_ctx = sha512_ctx_mgr_submit(cstate->mgr, sha_ctx,
> + sha_ctx = sha512_ctx_mgr_submit(cstate, sha_ctx,
> rctx->walk.data, nbytes, flag);
> if (!sha_ctx) {
> if (flush)
> - sha_ctx = sha512_ctx_mgr_flush(cstate->mgr);
> + sha_ctx = sha512_ctx_mgr_flush(cstate);
> }
> kernel_fpu_end();
> if (sha_ctx)
> @@ -471,11 +490,12 @@ static int sha_complete_job(struct mcryptd_hash_request_ctx *rctx,
> struct sha512_hash_ctx *sha_ctx;
> struct mcryptd_hash_request_ctx *req_ctx;
> int ret;
> + unsigned long flags;
>
> /* remove from work list */
> - spin_lock(&cstate->work_lock);
> + spin_lock_irqsave(&cstate->work_lock, flags);
> list_del(&rctx->waiter);
> - spin_unlock(&cstate->work_lock);
> + spin_unlock_irqrestore(&cstate->work_lock, flags);
>
> if (irqs_disabled())
> rctx->complete(&req->base, err);
> @@ -486,14 +506,14 @@ static int sha_complete_job(struct mcryptd_hash_request_ctx *rctx,
> }
>
> /* check to see if there are other jobs that are done */
> - sha_ctx = sha512_ctx_mgr_get_comp_ctx(cstate->mgr);
> + sha_ctx = sha512_ctx_mgr_get_comp_ctx(cstate);
> while (sha_ctx) {
> req_ctx = cast_hash_to_mcryptd_ctx(sha_ctx);
> ret = sha_finish_walk(&req_ctx, cstate, false);
> if (req_ctx) {
> - spin_lock(&cstate->work_lock);
> + spin_lock_irqsave(&cstate->work_lock, flags);
> list_del(&req_ctx->waiter);
> - spin_unlock(&cstate->work_lock);
> + spin_unlock_irqrestore(&cstate->work_lock, flags);
>
> req = cast_mcryptd_ctx_to_req(req_ctx);
> if (irqs_disabled())
> @@ -504,7 +524,7 @@ static int sha_complete_job(struct mcryptd_hash_request_ctx *rctx,
> local_bh_enable();
> }
> }
> - sha_ctx = sha512_ctx_mgr_get_comp_ctx(cstate->mgr);
> + sha_ctx = sha512_ctx_mgr_get_comp_ctx(cstate);
> }
>
> return 0;
> @@ -515,6 +535,7 @@ static void sha512_mb_add_list(struct mcryptd_hash_request_ctx *rctx,
> {
> unsigned long next_flush;
> unsigned long delay = usecs_to_jiffies(FLUSH_INTERVAL);
> + unsigned long flags;
>
> /* initialize tag */
> rctx->tag.arrival = jiffies; /* tag the arrival time */
> @@ -522,9 +543,9 @@ static void sha512_mb_add_list(struct mcryptd_hash_request_ctx *rctx,
> next_flush = rctx->tag.arrival + delay;
> rctx->tag.expire = next_flush;
>
> - spin_lock(&cstate->work_lock);
> + spin_lock_irqsave(&cstate->work_lock, flags);
> list_add_tail(&rctx->waiter, &cstate->work_list);
> - spin_unlock(&cstate->work_lock);
> + spin_unlock_irqrestore(&cstate->work_lock, flags);
>
> mcryptd_arm_flusher(cstate, delay);
> }
> @@ -565,7 +586,7 @@ static int sha512_mb_update(struct ahash_request *areq)
> sha_ctx = (struct sha512_hash_ctx *) ahash_request_ctx(areq);
> sha512_mb_add_list(rctx, cstate);
> kernel_fpu_begin();
> - sha_ctx = sha512_ctx_mgr_submit(cstate->mgr, sha_ctx, rctx->walk.data,
> + sha_ctx = sha512_ctx_mgr_submit(cstate, sha_ctx, rctx->walk.data,
> nbytes, HASH_UPDATE);
> kernel_fpu_end();
>
> @@ -628,7 +649,7 @@ static int sha512_mb_finup(struct ahash_request *areq)
> sha512_mb_add_list(rctx, cstate);
>
> kernel_fpu_begin();
> - sha_ctx = sha512_ctx_mgr_submit(cstate->mgr, sha_ctx, rctx->walk.data,
> + sha_ctx = sha512_ctx_mgr_submit(cstate, sha_ctx, rctx->walk.data,
> nbytes, flag);
> kernel_fpu_end();
>
> @@ -677,8 +698,7 @@ static int sha512_mb_final(struct ahash_request *areq)
> /* flag HASH_FINAL and 0 data size */
> sha512_mb_add_list(rctx, cstate);
> kernel_fpu_begin();
> - sha_ctx = sha512_ctx_mgr_submit(cstate->mgr, sha_ctx, &data, 0,
> - HASH_LAST);
> + sha_ctx = sha512_ctx_mgr_submit(cstate, sha_ctx, &data, 0, HASH_LAST);
> kernel_fpu_end();
>
> /* check if anything is returned */
> @@ -940,7 +960,7 @@ static unsigned long sha512_mb_flusher(struct mcryptd_alg_cstate *cstate)
> break;
> kernel_fpu_begin();
> sha_ctx = (struct sha512_hash_ctx *)
> - sha512_ctx_mgr_flush(cstate->mgr);
> + sha512_ctx_mgr_flush(cstate);
> kernel_fpu_end();
> if (!sha_ctx) {
> pr_err("sha512_mb error: nothing got flushed for"
> --
> 2.5.5
>
