Re: [PATCH net-next] ipv4: Fix refcount warning for new fib_info

On 8/2/21 11:58 AM, Matthieu Baerts wrote:

Hi David,

On 02/08/2021 18:02, David Ahern wrote:

quoted

Ioana reported a refcount warning when booting over NFS:

[    5.042532] ------------[ cut here ]------------
[    5.047184] refcount_t: addition on 0; use-after-free.
[    5.052324] WARNING: CPU: 7 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0xa4/0x150
...
[    5.167201] Call trace:
[    5.169635]  refcount_warn_saturate+0xa4/0x150
[    5.174067]  fib_create_info+0xc00/0xc90
[    5.177982]  fib_table_insert+0x8c/0x620
[    5.181893]  fib_magic.isra.0+0x110/0x11c
[    5.185891]  fib_add_ifaddr+0xb8/0x190
[    5.189629]  fib_inetaddr_event+0x8c/0x140

fib_treeref needs to be set after kzalloc. The old code had a ++ which
led to the confusion when the int was replaced by a refcount_t.

Thank you for the patch!

My CI was also complaining of not being able to run kernel selftests [1].
Your patch fixes the issue, thanks!

Tested-by: Matthieu Baerts <redacted>

Given how easily it is to trigger the warning, I get the impression the
original was an untested patch.