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| author | Yang Erkun <yangerkun@huawei.com> | 2024-10-21 22:23:41 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-12-09 10:33:08 +0100 |
| commit | 1cecfdbc6bfc89c516d286884c7f29267b95de2b (patch) | |
| tree | 0aff588f9286f97c2ed643702aa4800fc5448676 /fs | |
| parent | 2eb355346c5a2d767dfb21b3d1c4ea2d56cedb63 (diff) | |
| download | linux-1cecfdbc6bfc89c516d286884c7f29267b95de2b.tar.gz linux-1cecfdbc6bfc89c516d286884c7f29267b95de2b.tar.bz2 linux-1cecfdbc6bfc89c516d286884c7f29267b95de2b.zip | |
nfsd: make sure exp active before svc_export_show
commit be8f982c369c965faffa198b46060f8853e0f1f0 upstream.
The function `e_show` was called with protection from RCU. This only
ensures that `exp` will not be freed. Therefore, the reference count for
`exp` can drop to zero, which will trigger a refcount use-after-free
warning when `exp_get` is called. To resolve this issue, use
`cache_get_rcu` to ensure that `exp` remains active.
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 3 PID: 819 at lib/refcount.c:25
refcount_warn_saturate+0xb1/0x120
CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.16.1-2.fc37 04/01/2014
RIP: 0010:refcount_warn_saturate+0xb1/0x120
...
Call Trace:
<TASK>
e_show+0x20b/0x230 [nfsd]
seq_read_iter+0x589/0x770
seq_read+0x1e5/0x270
vfs_read+0x125/0x530
ksys_read+0xc1/0x160
do_syscall_64+0x5f/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fixes: bf18f163e89c ("NFSD: Using exp_get for export getting")
Cc: stable@vger.kernel.org # 4.20+
Signed-off-by: Yang Erkun <yangerkun@huawei.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/nfsd/export.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c index 2964bdae6392..d4d3ec58047e 100644 --- a/fs/nfsd/export.c +++ b/fs/nfsd/export.c @@ -1385,9 +1385,12 @@ static int e_show(struct seq_file *m, void *p) return 0; } - exp_get(exp); + if (!cache_get_rcu(&exp->h)) + return 0; + if (cache_check(cd, &exp->h, NULL)) return 0; + exp_put(exp); return svc_export_show(m, cd, cp); } |