CVE-2026-52985
Description
In the Linux kernel, the following vulnerability has been resolved:
netdevsim: zero initialize struct iphdr in dummy sk_buff
Syzbot reports a KMSAN uninit-value originating from
nsim_dev_trap_skb_build, with the allocation also
being performed in the same function.
Fix this by calling skb_put_zero instead of skb_put to
guarantee zero initialization of the whole IP header.
Summary dbcve.org
The netdevsim driver's nsim_dev_trap_skb_build function uses skb_put() to allocate memory for an IP header struct but fails to initialize it to zero, causing uninitialized kernel memory to be present in the sk_buff's iphdr structure. KMSAN detects this uninit-value bug. The fix is replacing skb_put with skb_put_zero to guarantee zero initialization of the entire IP header.
Mitigation
Apply the one-line code change to use skb_put_zero instead of skb_put in nsim_dev_trap_skb_build, then rebuild and test the netdevsim kernel module to verify the KMSAN warning is resolved.