netfilter: ebtables: fix table blob use-after-free

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ebtables: fix table blob use-after-free We are not allowed to return an error at this point. Looking at the code it looks like ret is always 0 at this point, but its not. t = find_table_lock(net, repl->name, &ret, &ebt_mutex); ... this can return a valid table, with ret != 0. This bug causes update of table->private with the new blob, but then frees the blob right away in the caller. Syzbot report: BUG: KASAN: vmalloc-out-of-bounds in __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 Read of size 4 at addr ffffc90005425000 by task kworker/u4:4/74 Workqueue: netns cleanup_net Call Trace: kasan_report+0xbf/0x1f0 mm/kasan/report.c:517 __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168 ebt_unregister_table+0x35/0x40 net/bridge/netfilter/ebtables.c:1372 ops_exit_list+0xb0/0x170 net/core/net_namespace.c:169 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613 ... ip(6)tables appears to be ok (ret should be 0 at this point) but make this more obvious.

References

• https://git.kernel.org/stable/c/9060abce3305ab2354c892c09d5689df51486df5
• https://git.kernel.org/stable/c/dbb3cbbf03b3c52cb390fabec357f1e4638004f5
• https://git.kernel.org/stable/c/3dd6ac973351308d4117eda32298a9f1d68764fd
• https://git.kernel.org/stable/c/cda0e0243bd3c04008fcd37a46b0269fb3c49249
• https://git.kernel.org/stable/c/e58a171d35e32e6e8c37cfe0e8a94406732a331f