tree ca07296f737721f6234967c3636748471c593c98
parent 9d5b95ce1488266fd3dc3951da6c8ce25c366ada
author Nikita Zhandarovich <n.zhandarovich@fintech.ru> 1712585439 -0700
committer Vegard Nossum <vegard.nossum@oracle.com> 1721068223 +0000

net/9p: fix uninit-value in p9_client_rpc()

commit 25460d6f39024cc3b8241b14c7ccf0d6f11a736a upstream.

Syzbot with the help of KMSAN reported the following error:

BUG: KMSAN: uninit-value in trace_9p_client_res include/trace/events/9p.h:146 [inline]
BUG: KMSAN: uninit-value in p9_client_rpc+0x1314/0x1340 net/9p/client.c:754
 trace_9p_client_res include/trace/events/9p.h:146 [inline]
 p9_client_rpc+0x1314/0x1340 net/9p/client.c:754
 p9_client_create+0x1551/0x1ff0 net/9p/client.c:1031
 v9fs_session_init+0x1b9/0x28e0 fs/9p/v9fs.c:410
 v9fs_mount+0xe2/0x12b0 fs/9p/vfs_super.c:122
 legacy_get_tree+0x114/0x290 fs/fs_context.c:662
 vfs_get_tree+0xa7/0x570 fs/super.c:1797
 do_new_mount+0x71f/0x15e0 fs/namespace.c:3352
 path_mount+0x742/0x1f20 fs/namespace.c:3679
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x725/0x810 fs/namespace.c:3875
 __x64_sys_mount+0xe4/0x150 fs/namespace.c:3875
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Uninit was created at:
 __alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598
 __alloc_pages_node include/linux/gfp.h:238 [inline]
 alloc_pages_node include/linux/gfp.h:261 [inline]
 alloc_slab_page mm/slub.c:2175 [inline]
 allocate_slab mm/slub.c:2338 [inline]
 new_slab+0x2de/0x1400 mm/slub.c:2391
 ___slab_alloc+0x1184/0x33d0 mm/slub.c:3525
 __slab_alloc mm/slub.c:3610 [inline]
 __slab_alloc_node mm/slub.c:3663 [inline]
 slab_alloc_node mm/slub.c:3835 [inline]
 kmem_cache_alloc+0x6d3/0xbe0 mm/slub.c:3852
 p9_tag_alloc net/9p/client.c:278 [inline]
 p9_client_prepare_req+0x20a/0x1770 net/9p/client.c:641
 p9_client_rpc+0x27e/0x1340 net/9p/client.c:688
 p9_client_create+0x1551/0x1ff0 net/9p/client.c:1031
 v9fs_session_init+0x1b9/0x28e0 fs/9p/v9fs.c:410
 v9fs_mount+0xe2/0x12b0 fs/9p/vfs_super.c:122
 legacy_get_tree+0x114/0x290 fs/fs_context.c:662
 vfs_get_tree+0xa7/0x570 fs/super.c:1797
 do_new_mount+0x71f/0x15e0 fs/namespace.c:3352
 path_mount+0x742/0x1f20 fs/namespace.c:3679
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x725/0x810 fs/namespace.c:3875
 __x64_sys_mount+0xe4/0x150 fs/namespace.c:3875
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

If p9_check_errors() fails early in p9_client_rpc(), req->rc.tag
will not be properly initialized. However, trace_9p_client_res()
ends up trying to print it out anyway before p9_client_rpc()
finishes.

Fix this issue by assigning default values to p9_fcall fields
such as 'tag' and (just in case KMSAN unearths something new) 'id'
during the tag allocation stage.

Reported-and-tested-by: syzbot+ff14db38f56329ef68df@syzkaller.appspotmail.com
Fixes: 348b59012e5c ("net/9p: Convert net/9p protocol dumps to tracepoints")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Cc: stable@vger.kernel.org
Message-ID: <20240408141039.30428-1-n.zhandarovich@fintech.ru>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 72c5d8e416ecc46af370a1340b3db5ff0b0cc867)
[Vegard: fix conflicts due to missing commits
 1555583b63b344c634bbaaf6d966923d3fe96d44 ("9p: embed fcall in req to
 round down buffer allocs") and be87f21e6b25e3b09eb913dd4f8e416a2a81a3a0
 ("9p: add a per-client fcall kmem_cache").]
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>