[PATCH net] net: nfc: llcp: Add lock when modifying device list

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>
---
 net/nfc/llcp_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index f60e424e0607..6705bb895e23 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c

@@ -1636,7 +1636,9 @@ int nfc_llcp_register_device(struct nfc_dev *ndev)
 	timer_setup(&local->sdreq_timer, nfc_llcp_sdreq_timer, 0);
 	INIT_WORK(&local->sdreq_timeout_work, nfc_llcp_sdreq_timeout_work);
 
+	spin_lock(&llcp_devices_lock);
 	list_add(&local->list, &llcp_devices);
+	spin_unlock(&llcp_devices_lock);
 
 	return 0;
 }

-- 
2.41.0

On Fri, Sep 08, 2023 at 07:58:53PM -0400, Jeremy Cline wrote:

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>

Hi Jeremy,

thanks for your patch.

I don't think you need to resubmit for this,
I think this patch warrants a fixes tag:

Fixes: d646960f7986 ("NFC: Initial LLCP support")

Otherwise, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

On Sun, Sep 10, 2023 at 05:28:12PM +0200, Simon Horman wrote:

On Fri, Sep 08, 2023 at 07:58:53PM -0400, Jeremy Cline wrote:

quoted

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>

Hi Jeremy,

thanks for your patch.

I don't think you need to resubmit for this,
I think this patch warrants a fixes tag:

Fixes: d646960f7986 ("NFC: Initial LLCP support")

My bad, indeed. The lock in question looks to have been added in
6709d4b7bc2e ("net: nfc: Fix use-after-free caused by
nfc_llcp_find_local") which itself includes a couple fix tags, should
this reference that commit instead as it won't backport without that
one?

Otherwise, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

Thanks,
Jeremy

On Sun, Sep 10, 2023 at 07:06:19PM -0400, Jeremy Cline wrote:

On Sun, Sep 10, 2023 at 05:28:12PM +0200, Simon Horman wrote:

quoted

On Fri, Sep 08, 2023 at 07:58:53PM -0400, Jeremy Cline wrote:

quoted

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>

Hi Jeremy,

thanks for your patch.

I don't think you need to resubmit for this,
I think this patch warrants a fixes tag:

Fixes: d646960f7986 ("NFC: Initial LLCP support")

My bad, indeed. The lock in question looks to have been added in
6709d4b7bc2e ("net: nfc: Fix use-after-free caused by
nfc_llcp_find_local") which itself includes a couple fix tags, should
this reference that commit instead as it won't backport without that
one?

Yes, I think that is likely.
Sorry for not noticing that.

quoted

Otherwise, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

Thanks,
Jeremy

On Mon, Sep 11, 2023 at 07:59:04AM +0200, Simon Horman wrote:

On Sun, Sep 10, 2023 at 07:06:19PM -0400, Jeremy Cline wrote:

quoted

On Sun, Sep 10, 2023 at 05:28:12PM +0200, Simon Horman wrote:

quoted

On Fri, Sep 08, 2023 at 07:58:53PM -0400, Jeremy Cline wrote:

quoted

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>

Hi Jeremy,

thanks for your patch.

I don't think you need to resubmit for this,
I think this patch warrants a fixes tag:

Fixes: d646960f7986 ("NFC: Initial LLCP support")

My bad, indeed. The lock in question looks to have been added in
6709d4b7bc2e ("net: nfc: Fix use-after-free caused by
nfc_llcp_find_local") which itself includes a couple fix tags, should
this reference that commit instead as it won't backport without that
one?

Yes, I think that is likely.
Sorry for not noticing that.

And further, sorry for being vague in my previous email.
Having now looked over 6709d4b7bc2e I agree it is
the correct commit for a fixes tag for this patch.

quoted

quoted

Otherwise, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

Thanks,
Jeremy

On Mon, Sep 11, 2023 at 02:52:51PM +0200, Simon Horman wrote:

On Mon, Sep 11, 2023 at 07:59:04AM +0200, Simon Horman wrote:

quoted

On Sun, Sep 10, 2023 at 07:06:19PM -0400, Jeremy Cline wrote:

quoted

On Sun, Sep 10, 2023 at 05:28:12PM +0200, Simon Horman wrote:

quoted

On Fri, Sep 08, 2023 at 07:58:53PM -0400, Jeremy Cline wrote:

quoted

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>

Hi Jeremy,

thanks for your patch.

I don't think you need to resubmit for this,
I think this patch warrants a fixes tag:

Fixes: d646960f7986 ("NFC: Initial LLCP support")

My bad, indeed. The lock in question looks to have been added in
6709d4b7bc2e ("net: nfc: Fix use-after-free caused by
nfc_llcp_find_local") which itself includes a couple fix tags, should
this reference that commit instead as it won't backport without that
one?

Yes, I think that is likely.
Sorry for not noticing that.

And further, sorry for being vague in my previous email.
Having now looked over 6709d4b7bc2e I agree it is
the correct commit for a fixes tag for this patch.

Super, thanks. If it's helpful I can re-roll the patch, otherwise I'll
just leave it as-is.

Thanks,
Jeremy

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski [off-list ref]:

On Fri,  8 Sep 2023 19:58:53 -0400 you wrote:

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Signed-off-by: Jeremy Cline <redacted>

[...]

Here is the summary with links:
  - [net] net: nfc: llcp: Add lock when modifying device list
    https://git.kernel.org/netdev/net/c/dfc7f7a988da

You are awesome, thank you!
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