Re: [PATCH] net: wireless: util: Fix uninitialized header access in cfg80211_classify8021d

[Johannes Berg]

On Mon, 2025-11-03 at 00:02 +0530, Ranganath V N wrote:
> Fix an issue detected by  syzbot with KMSAN
> BUG: KMSAN: uninit-value in cfg80211_classify8021d+0x99d/0x12b0
> net/wireless/util.c:1027
> 
> The function accessed DSCP fields from IP and IPv6 headers without first
> verifying that sufficient header data was present in the skb. When a
> packet reaches this path, the header dereference could access
> uninitialized memory, as reported by KMSAN under fuzzing with syzkaller.
> 
> Add explicit pskb_may_pull() checks for both IPv4 and IPv6 headers to
> ensure that the required header data is available before extracting the
> DSCP field. This prevents uninitialized memory reads while preserving
> existing behavior for valid packets
> 
> This fix has been tested and validated by syzbot. This patch closes the
> bug reported at the following syzkaller link.Fixes the uninitialized
> header access.
> 
> Reported-by: syzbot+878ddc3962f792e9af59@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com./bug?extid=878ddc3962f792e9af59
> Tested-by: syzbot+878ddc3962f792e9af59@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: b156579b1404 ("Treat IPv6 diffserv the same as IPv4 for 802.11e")

Commit: 6132cdec43a5 ("net: wireless: util: Fix uninitialized header
access in cfg80211_classify8021d")
	Fixes tag: Fixes: b156579b1404 ("Treat IPv6 diffserv the same as IPv4 for 802.11e")
	Has these problem(s):
		- Subject does not match target commit subject
		  Just use
			git log -1 --format='Fixes: %h ("%s")'


Subject also needs to be adjusted.

johannes