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
Fixes: 6709d4b7bc2e ("net: nfc: Fix use-after-free caused by nfc_llcp_find_local")
Signed-off-by: Jeremy Cline <jeremy@jcline.org>
---
Changes from v1: added the correct Fixes tag

 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

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 25 Sep 2023 15:23:51 -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
> Fixes: 6709d4b7bc2e ("net: nfc: Fix use-after-free caused by nfc_llcp_find_local")
> Signed-off-by: Jeremy Cline <jeremy@jcline.org>
> 
> [...]

Here is the summary with links:
  - [v2,net] net: nfc: llcp: Add lock when modifying device list
    https://git.kernel.org/netdev/net/c/dfc7f7a988da

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

On 25/09/2023 21:23, 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
> Fixes: 6709d4b7bc2e ("net: nfc: Fix use-after-free caused by nfc_llcp_find_local")
> Signed-off-by: Jeremy Cline <jeremy@jcline.org>
> ---


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

On Mon, Sep 25, 2023 at 03:23:51PM -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
> Fixes: 6709d4b7bc2e ("net: nfc: Fix use-after-free caused by nfc_llcp_find_local")
> Signed-off-by: Jeremy Cline <jeremy@jcline.org>

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