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authorEric Dumazet <edumazet@google.com>2020-01-22 09:07:35 -0800
committerDavid S. Miller <davem@davemloft.net>2020-01-23 11:42:44 +0100
commit1efba987c48629c0c64703bb4ea76ca1a3771d17 (patch)
tree0bdb2a5ca6a7059cdba16ed9b163b485f431f171 /drivers
parent971de2e572118c1128bff295341e37b6c8b8f108 (diff)
tun: add mutex_unlock() call and napi.skb clearing in tun_get_user()
If both IFF_NAPI_FRAGS mode and XDP are enabled, and the XDP program consumes the skb, we need to clear the napi.skb (or risk a use-after-free) and release the mutex (or risk a deadlock) WARNING: lock held when returning to user space! 5.5.0-rc6-syzkaller #0 Not tainted ------------------------------------------------ syz-executor.0/455 is leaving the kernel with locks still held! 1 lock held by syz-executor.0/455: #0: ffff888098f6e748 (&tfile->napi_mutex){+.+.}, at: tun_get_user+0x1604/0x3fc0 drivers/net/tun.c:1835 Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Cc: Petar Penkov <ppenkov@google.com> Cc: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/net/tun.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 683d371e6e82..35e884a8242d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1936,6 +1936,10 @@ drop:
if (ret != XDP_PASS) {
rcu_read_unlock();
local_bh_enable();
+ if (frags) {
+ tfile->napi.skb = NULL;
+ mutex_unlock(&tfile->napi_mutex);
+ }
return total_len;
}
}