BUG: sleeping function called from invalid context at crypto/skcipher.c:LINE

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e0a092eb Merge branch 'smc-next'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=139878f3200000
kernel config: https://syzkaller.appspot.com/x/.config?x=94c460c3e4cd188a
dashboard link: https://syzkaller.appspot.com/bug?extid=6f72c20560060c98b566
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6f72c2...@syzkaller.appspotmail.com

BUG: sleeping function called from invalid context at crypto/skcipher.c:477
in_atomic(): 1, irqs_disabled(): 0, pid: 12, name: kworker/0:1
2 locks held by kworker/0:1/12:
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at: __write_once_size
include/linux/compiler.h:220 [inline]
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at: arch_atomic64_set
arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:855 [inline]
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at: atomic_long_set
include/asm-generic/atomic-long.h:40 [inline]
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at: set_work_data
kernel/workqueue.c:619 [inline]
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: 000000000864d9ff ((wq_completion)crypto){+.+.}, at:
process_one_work+0x87e/0x1790 kernel/workqueue.c:2240
#1: 000000008b3d6218 ((work_completion)(&cpu_queue->work)){+.+.}, at:
process_one_work+0x8b4/0x1790 kernel/workqueue.c:2244
Preemption disabled at:
[<ffffffff830d4130>] local_bh_disable include/linux/bottom_half.h:19
[inline]
[<ffffffff830d4130>] cryptd_skcipher_complete+0x90/0x170 crypto/cryptd.c:471
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc4+ #135
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: crypto cryptd_queue_worker
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
___might_sleep.cold+0x1bd/0x1f6 kernel/sched/core.c:6190
__might_sleep+0x95/0x190 kernel/sched/core.c:6143
skcipher_walk_virt+0x11e/0x150 crypto/skcipher.c:477
xor_tweak+0x146/0x350 crypto/xts.c:105
xor_tweak_post crypto/xts.c:133 [inline]
crypt_done+0x87/0xa0 crypto/xts.c:141
cryptd_skcipher_complete+0xbf/0x170 crypto/cryptd.c:472
cryptd_skcipher_decrypt+0x2f7/0x420 crypto/cryptd.c:532
cryptd_queue_worker+0x126/0x1f0 crypto/cryptd.c:193
process_one_work+0x98e/0x1790 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x357/0x430 kernel/kthread.c:253
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352


---
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[Herbert Xu]

Thanks for the report. Please try this patch:

---8<---
When we perform a walk in the completion function, we need to ensure
that it is atomic.

Reported-by: syzbot+6f72c2...@syzkaller.appspotmail.com
Fixes: 78105c7e769b ("crypto: xts - Drop use of auxiliary buffer")
Cc: <sta...@vger.kernel.org>
Signed-off-by: Herbert Xu <her...@gondor.apana.org.au>

diff --git a/crypto/xts.c b/crypto/xts.c
index 847f54f76789..c915a45711f5 100644
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -88,7 +88,8 @@ static int setkey(struct crypto_skcipher *parent, const u8 *key,
* mutliple calls to the 'ecb(..)' instance, which usually would be slower than
* just doing the gf128mul_x_ble() calls again.
*/
-static int xor_tweak(struct skcipher_request *req, bool second_pass)
+static int xor_tweak(struct skcipher_request *req, bool second_pass,
+ bool atomic)
{
struct rctx *rctx = skcipher_request_ctx(req);
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
@@ -102,7 +103,7 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)
/* set to our TFM to enforce correct alignment: */
skcipher_request_set_tfm(req, tfm);
}
- err = skcipher_walk_virt(&w, req, false);
+ err = skcipher_walk_virt(&w, req, atomic);

while (w.nbytes) {
unsigned int avail = w.nbytes;
@@ -125,12 +126,12 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)

static int xor_tweak_pre(struct skcipher_request *req)
{
- return xor_tweak(req, false);
+ return xor_tweak(req, false, false);
}

-static int xor_tweak_post(struct skcipher_request *req)
+static int xor_tweak_post(struct skcipher_request *req, bool atomic)
{
- return xor_tweak(req, true);
+ return xor_tweak(req, true, atomic);
}

static void crypt_done(struct crypto_async_request *areq, int err)
@@ -138,7 +139,7 @@ static void crypt_done(struct crypto_async_request *areq, int err)
struct skcipher_request *req = areq->data;

if (!err)
- err = xor_tweak_post(req);
+ err = xor_tweak_post(req, true);

skcipher_request_complete(req, err);
}
@@ -166,7 +167,7 @@ static int encrypt(struct skcipher_request *req)
init_crypt(req);
return xor_tweak_pre(req) ?:
crypto_skcipher_encrypt(subreq) ?:
- xor_tweak_post(req);
+ xor_tweak_post(req, false);
}

static int decrypt(struct skcipher_request *req)
@@ -177,7 +178,7 @@ static int decrypt(struct skcipher_request *req)
init_crypt(req);
return xor_tweak_pre(req) ?:
crypto_skcipher_decrypt(subreq) ?:
- xor_tweak_post(req);
+ xor_tweak_post(req, false);
}

static int init_tfm(struct crypto_skcipher *tfm)
--
Email: Herbert Xu <her...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[Eric Biggers]

Hi Herbert,

This isn't correct because skcipher_walk_virt() can still sleep when
atomic=true, since it may need to copy the IV. That's why I added might_sleep()
to it in commit bb648291fc04, and that's what's triggering here.

This is the correct fix:

diff --git a/crypto/xts.c b/crypto/xts.c
index aed11e63ca315..359ef15e1673e 100644
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -101,6 +101,7 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)
req = &rctx->subreq;

/* set to our TFM to enforce correct alignment: */
skcipher_request_set_tfm(req, tfm);

+ req->base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;

}
err = skcipher_walk_virt(&w, req, false);

Likewise for LRW.

With the crypto self-tests and CONFIG_DEBUG_ATOMIC_SLEEP enabled, this bug can
be reproduced by trying to allocate the skcipher algorithm
"xts(cryptd(ecb(aes-generic)))", e.g. by running in Python:

import socket

fd = socket.socket(socket.AF_ALG, 5, 0)
fd.bind(("skcipher", "xts(cryptd(ecb(aes-generic)))"))

Likewise, use "lrw(cryptd(ecb(aes-generic)))" for LRW.

- Eric

[Herbert Xu]

When we perform a walk in the completion function, we need to ensure
that it is atomic.

Reported-by: syzbot+6f72c2...@syzkaller.appspotmail.com
Fixes: 78105c7e769b ("crypto: xts - Drop use of auxiliary buffer")
Cc: <sta...@vger.kernel.org>
Signed-off-by: Herbert Xu <her...@gondor.apana.org.au>

diff --git a/crypto/xts.c b/crypto/xts.c

index 847f54f76789..2f948328cabb 100644
--- a/crypto/xts.c
+++ b/crypto/xts.c
@@ -137,8 +137,12 @@ static void crypt_done(struct crypto_async_request *areq, int err)

{
struct skcipher_request *req = areq->data;

- if (!err)
+ if (!err) {
+ struct rctx *rctx = skcipher_request_ctx(req);
+
+ rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
err = xor_tweak_post(req);
+ }

skcipher_request_complete(req, err);

[Herbert Xu]

On Sun, Apr 14, 2019 at 09:35:13AM -0700, Eric Biggers wrote:
>
> This isn't correct because skcipher_walk_virt() can still sleep when
> atomic=true, since it may need to copy the IV. That's why I added might_sleep()
> to it in commit bb648291fc04, and that's what's triggering here.

Thanks for catching this Eric!

> This is the correct fix:
>
> diff --git a/crypto/xts.c b/crypto/xts.c
> index aed11e63ca315..359ef15e1673e 100644
> --- a/crypto/xts.c
> +++ b/crypto/xts.c
> @@ -101,6 +101,7 @@ static int xor_tweak(struct skcipher_request *req, bool second_pass)
> req = &rctx->subreq;
> /* set to our TFM to enforce correct alignment: */
> skcipher_request_set_tfm(req, tfm);
> + req->base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
> }

This is what I'm doing in v2, except I've moved it over to
crypt_done so that we don't affect the synchronous path.

Cheers,

[Ondrej Mosnacek]

On Mon, Apr 15, 2019 at 8:35 AM Herbert Xu <her...@gondor.apana.org.au> wrote:
> When we perform a walk in the completion function, we need to ensure
> that it is atomic.
>
> Reported-by: syzbot+6f72c2...@syzkaller.appspotmail.com
> Fixes: 78105c7e769b ("crypto: xts - Drop use of auxiliary buffer")
> Cc: <sta...@vger.kernel.org>
> Signed-off-by: Herbert Xu <her...@gondor.apana.org.au>

Acked-by: Ondrej Mosnacek <omos...@redhat.com>

>
> diff --git a/crypto/xts.c b/crypto/xts.c
> index 847f54f76789..2f948328cabb 100644
> --- a/crypto/xts.c
> +++ b/crypto/xts.c
> @@ -137,8 +137,12 @@ static void crypt_done(struct crypto_async_request *areq, int err)
> {
> struct skcipher_request *req = areq->data;
>
> - if (!err)
> + if (!err) {
> + struct rctx *rctx = skcipher_request_ctx(req);
> +
> + rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
> err = xor_tweak_post(req);
> + }
>
> skcipher_request_complete(req, err);
> }
> --
> Email: Herbert Xu <her...@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.