title: net: fix use-after-free in tw_timer_handler
description: In the Linux kernel, the following vulnerability has been resolved:
net: fix use-after-free in tw_timer_handler
A real world panic issue was found as follow in Linux 5.4.
BUG: unable to handle page fault for address: ffffde49a863de28
PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0
RIP: 0010:tw_timer_handler+0x20/0x40
Call Trace:
<IRQ>
call_timer_fn+0x2b/0x120
run_timer_softirq+0x1ef/0x450
__do_softirq+0x10d/0x2b8
irq_exit+0xc7/0xd0
smp_apic_timer_interrupt+0x68/0x120
apic_timer_interrupt+0xf/0x20
This issue was also reported since 2017 in the thread [1],
unfortunately, the issue was still can be reproduced after fixing
DCCP.
The ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net
namespace is destroyed since tcp_sk_ops is registered befrore
ipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops
in the list of pernet_list. There will be a use-after-free on
net->mib.net_statistics in tw_timer_handler after ipv4_mib_exit_net
if there are some inflight time-wait timers.
This bug is not introduced by commit f2bf415cfed7 ("mib: add net to
NET_ADD_STATS_BH") since the net_statistics is a global variable
instead of dynamic allocation and freeing. Actually, commit
61a7e26028b9 ("mib: put net statistics on struct net") introduces
the bug since it put net statistics on struct net and free it when
net namespace is destroyed.
Moving init_ipv4_mibs() to the front of tcp_init() to fix this bug
and replace pr_crit() with panic() since continuing is meaningless
when init_ipv4_mibs() fails.
[1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1
affected:
{
product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 61a7e26028b9, lessThan: 15579e1301f8, status: affected, versionType: git
version: 61a7e26028b9, lessThan: e73164e89d1b, status: affected, versionType: git
version: 61a7e26028b9, lessThan: 5c2fe20ad37f, status: affected, versionType: git
version: 61a7e26028b9, lessThan: a8e1944b44f9, status: affected, versionType: git
version: 61a7e26028b9, lessThan: fe5838c22b98, status: affected, versionType: git
version: 61a7e26028b9, lessThan: 2386e81a1d27, status: affected, versionType: git
version: 61a7e26028b9, lessThan: 08eacbd141e2, status: affected, versionType: git
version: 61a7e26028b9, lessThan: e22e45fc9e41, status: affected, versionType: git
}
{
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 2.6.27, status: affected
version: 0, lessThan: 2.6.27, status: unaffected, versionType: custom
version: 4.4.298, lessThanOrEqual: 4.4.*, status: unaffected, versionType: custom
version: 4.9.296, lessThanOrEqual: 4.9.*, status: unaffected, versionType: custom
version: 4.14.261, lessThanOrEqual: 4.14.*, status: unaffected, versionType: custom
version: 4.19.224, lessThanOrEqual: 4.19.*, status: unaffected, versionType: custom
version: 5.4.170, lessThanOrEqual: 5.4.*, status: unaffected, versionType: custom
version: 5.10.90, lessThanOrEqual: 5.10.*, status: unaffected, versionType: custom
version: 5.15.13, lessThanOrEqual: 5.15.*, status: unaffected, versionType: custom
version: 5.16, lessThanOrEqual: *, status: unaffected, versionType: original_commit_for_fix
}
