On Thu, Jul 27, 2023 at 07:15:54PM +0000, Rishabh Bhatnagar wrote:
From: Lee Jones lee@kernel.org
Upstream commit 04c55383fa5689357bcdd2c8036725a55ed632bc.
In the event of a failure in tcf_change_indev(), u32_set_parms() will immediately return without decrementing the recently incremented reference counter. If this happens enough times, the counter will rollover and the reference freed, leading to a double free which can be used to do 'bad things'.
In order to prevent this, move the point of possible failure above the point where the reference counter is incremented. Also save any meaningful return values to be applied to the return data at the appropriate point in time.
This issue was caught with KASAN.
Fixes: 705c7091262d ("net: sched: cls_u32: no need to call tcf_exts_change for newly allocated struct") Suggested-by: Eric Dumazet edumazet@google.com Signed-off-by: Lee Jones lee@kernel.org Reviewed-by: Eric Dumazet edumazet@google.com Acked-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Rishabh Bhatnagar risbhat@amazon.com
net/sched/cls_u32.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
We need a 4.19.y backport before we can apply a 4.14.y version, as you do not want to upgrade and have a regression.
thanks,
greg k-h