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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	syzbot <syzbot+6455648abc28dbdd1e7f@syzkaller.appspotmail.com>,
	keyrings@vger.kernel.org,
	LSM List <linux-security-module@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: WARNING: refcount bug in find_key_to_update
Date: Fri, 18 Oct 2019 10:54:07 +0000	[thread overview]
Message-ID: <b211005b-75de-7936-c97a-817f7100415a@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20191017160028.GA726@sol.localdomain>

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On 2019/10/18 1:00, Eric Biggers wrote:
> The key is supposed to have refcount >= 1 since it's in a keyring.
> So some bug is causing it to have refcount 0.  Perhaps some place calling
> key_put() too many times.
> 
> Unfortunately I can't get the reproducer to work locally.
> 
> Note that there are 2 other syzbot reports that look related.
> No reproducers for them, though:
> 
> Title:              KASAN: use-after-free Read in key_put
> Last occurred:      1 day ago
> Reported:           28 days ago
> Branches:           Mainline
> Dashboard link:     https://syzkaller.appspot.com/bug?idñ3750b1124e01191250cf930086dcc40740fa30
> Original thread:    https://lore.kernel.org/lkml/0000000000008c3e590592cf4b7f@google.com/T/#u
> 
> Title:              KASAN: use-after-free Read in keyring_compare_object
> Last occurred:      49 days ago
> Reported:           84 days ago
> Branches:           Mainline
> Dashboard link:     https://syzkaller.appspot.com/bug?idR9ab6a98286c2a97c445988a62760a58d4a1d4b
> Original thread:    https://lore.kernel.org/lkml/000000000000038ef6058e6f3592@google.com/T/#u
> 

I don't know about keys, but I rather suspect lack of serialization locks between
"looking up for checking existing keys" versus "looking up for garbage collection".
Can we dump locks held by current thread when panic() is called?

WARNING: multiple messages have this Message-ID (diff)
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	syzbot <syzbot+6455648abc28dbdd1e7f@syzkaller.appspotmail.com>,
	keyrings@vger.kernel.org,
	LSM List <linux-security-module@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: WARNING: refcount bug in find_key_to_update
Date: Fri, 18 Oct 2019 19:54:07 +0900	[thread overview]
Message-ID: <b211005b-75de-7936-c97a-817f7100415a@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20191017160028.GA726@sol.localdomain>

On 2019/10/18 1:00, Eric Biggers wrote:
> The key is supposed to have refcount >= 1 since it's in a keyring.
> So some bug is causing it to have refcount 0.  Perhaps some place calling
> key_put() too many times.
> 
> Unfortunately I can't get the reproducer to work locally.
> 
> Note that there are 2 other syzbot reports that look related.
> No reproducers for them, though:
> 
> Title:              KASAN: use-after-free Read in key_put
> Last occurred:      1 day ago
> Reported:           28 days ago
> Branches:           Mainline
> Dashboard link:     https://syzkaller.appspot.com/bug?id=f13750b1124e01191250cf930086dcc40740fa30
> Original thread:    https://lore.kernel.org/lkml/0000000000008c3e590592cf4b7f@google.com/T/#u
> 
> Title:              KASAN: use-after-free Read in keyring_compare_object
> Last occurred:      49 days ago
> Reported:           84 days ago
> Branches:           Mainline
> Dashboard link:     https://syzkaller.appspot.com/bug?id=529ab6a98286c2a97c445988a62760a58d4a1d4b
> Original thread:    https://lore.kernel.org/lkml/000000000000038ef6058e6f3592@google.com/T/#u
> 

I don't know about keys, but I rather suspect lack of serialization locks between
"looking up for checking existing keys" versus "looking up for garbage collection".
Can we dump locks held by current thread when panic() is called?


  reply	other threads:[~2019-10-18 10:54 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17  1:42 WARNING: refcount bug in find_key_to_update syzbot
2019-10-17  1:42 ` syzbot
2019-10-17  2:42 ` syzbot
2019-10-17  2:42   ` syzbot
2019-10-17  2:42   ` syzbot
2019-10-17 15:53   ` Linus Torvalds
2019-10-17 15:53     ` Linus Torvalds
2019-10-17 15:53     ` Linus Torvalds
2019-10-17 16:00     ` Eric Biggers
2019-10-17 16:00       ` Eric Biggers
2019-10-17 16:00       ` Eric Biggers
2019-10-18 10:54       ` Tetsuo Handa [this message]
2019-10-18 10:54         ` Tetsuo Handa
2019-10-18 16:45       ` David Howells
2019-10-18 16:45         ` David Howells
2019-10-18 16:38   ` David Howells
2019-10-18 16:38     ` David Howells
2019-10-18 16:38     ` David Howells
2019-10-22 10:35   ` David Howells
2019-10-22 10:35     ` David Howells
2019-10-22 10:35     ` David Howells
2019-10-22 13:17   ` David Howells
2019-10-22 13:17     ` David Howells
2019-10-22 13:17     ` David Howells
2019-10-21 15:59 ` David Howells
2019-10-21 15:59   ` David Howells
2019-10-21 16:05   ` Dmitry Vyukov
2019-10-21 16:05     ` Dmitry Vyukov
     [not found] <20191017092428.7336-1-hdanton@sina.com>
2019-10-18 16:46 ` David Howells
2019-10-18 16:46   ` David Howells

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