CVE-2026-64061

In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix early put of sink folio in netfs_read_gaps()

Fix netfs_read_gaps() to release the sink page it uses after waiting for

the request to complete. The way the sink page is used is that an

ITER_BVEC-class iterator is created that has the gaps from the target folio

at either end, but has the sink page tiled over the middle so that a single

read op can fill in both gaps.

The bug was found by KASAN detecting a UAF on the generic/075 xfstest in

the cifsd kernel thread that handles reception of data from the TCP socket:

BUG: KASAN: use-after-free in _copy_to_iter+0x48a/0xa20

Write of size 885 at addr ffff888107f92000 by task cifsd/1285

CPU: 2 UID: 0 PID: 1285 Comm: cifsd Not tainted 7.0.0 #6 PREEMPT(lazy)

Call Trace:

dump_stack_lvl+0x5d/0x80

print_report+0x17f/0x4f1

kasan_report+0x100/0x1e0

kasan_check_range+0x10f/0x1e0

__asan_memcpy+0x3c/0x60

_copy_to_iter+0x48a/0xa20

__skb_datagram_iter+0x2c9/0x430

skb_copy_datagram_iter+0x6e/0x160

tcp_recvmsg_locked+0xce0/0x1130

tcp_recvmsg+0xeb/0x300

inet_recvmsg+0xcf/0x3a0

sock_recvmsg+0xea/0x100

cifs_readv_from_socket+0x3a6/0x4d0 [cifs]

cifs_read_iter_from_socket+0xdd/0x130 [cifs]

cifs_readv_receive+0xaad/0xb10 [cifs]

cifs_demultiplex_thread+0x1148/0x1740 [cifs]

kthread+0x1cf/0x210