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Date: Fri, 5 Apr 2024 04:35:40 -0700
From: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
To: Eric Van Hensbergen <ericvh@...nel.org>
CC: Nikita Zhandarovich <n.zhandarovich@...tech.ru>, Latchesar Ionkov
<lucho@...kov.net>, Dominique Martinet <asmadeus@...ewreck.org>, "Christian
Schoenebeck" <linux_oss@...debyte.com>, <v9fs@...ts.linux.dev>,
<linux-kernel@...r.kernel.org>, <lvc-project@...uxtesting.org>,
<syzbot+ff14db38f56329ef68df@...kaller.appspotmail.com>
Subject: [PATCH net] net/9p: fix uninit-value in p9_client_rpc()
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@...kaller.appspotmail.com
Fixes: 348b59012e5c ("net/9p: Convert net/9p protocol dumps to tracepoints")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
---
P.S. Not entirely sure that 'Fixes' tag is fully correct here.
net/9p/client.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/9p/client.c b/net/9p/client.c
index e265a0ca6bdd..a9d613af7455 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -235,6 +235,8 @@ static int p9_fcall_init(struct p9_client *c, struct p9_fcall *fc,
if (!fc->sdata)
return -ENOMEM;
fc->capacity = alloc_msize;
+ fc->id = 0;
+ fc->tag = 0;
return 0;
}
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