diff options
| author | Yang Erkun <yangerkun@huawei.com> | 2024-10-21 22:23:42 +0800 |
|---|---|---|
| committer | Chuck Lever <chuck.lever@oracle.com> | 2024-11-18 20:23:05 -0500 |
| commit | 2862eee078a4d2d1f584e7f24fa50dddfa5f3471 (patch) | |
| tree | 5d850bd9e07e5845202eac660f7e0f0381a0e8a3 | |
| parent | be8f982c369c965faffa198b46060f8853e0f1f0 (diff) | |
SUNRPC: make sure cache entry active before cache_show
The function `c_show` was called with protection from RCU. This only
ensures that `cp` will not be freed. Therefore, the reference count for
`cp` can drop to zero, which will trigger a refcount use-after-free
warning when `cache_get` is called. To resolve this issue, use
`cache_get_rcu` to ensure that `cp` remains active.
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 7 PID: 822 at lib/refcount.c:25
refcount_warn_saturate+0xb1/0x120
CPU: 7 UID: 0 PID: 822 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>
c_show+0x2fc/0x380 [sunrpc]
seq_read_iter+0x589/0x770
seq_read+0x1e5/0x270
proc_reg_read+0xe1/0x140
vfs_read+0x125/0x530
ksys_read+0xc1/0x160
do_syscall_64+0x5f/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Cc: stable@vger.kernel.org # v4.20+
Signed-off-by: Yang Erkun <yangerkun@huawei.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
| -rw-r--r-- | net/sunrpc/cache.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index 1bd3e531b0e0..059f6ef1ad18 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -1427,7 +1427,9 @@ static int c_show(struct seq_file *m, void *p) seq_printf(m, "# expiry=%lld refcnt=%d flags=%lx\n", convert_to_wallclock(cp->expiry_time), kref_read(&cp->ref), cp->flags); - cache_get(cp); + if (!cache_get_rcu(cp)) + return 0; + if (cache_check(cd, cp, NULL)) /* cache_check does a cache_put on failure */ seq_puts(m, "# "); |