Apparently a refactoring patch brought a bug, that was caught
by syzbot [1]
Original code was correct, do not try to be smarter than the
compiler :/
[1]
BUG: KASAN: slab-out-of-bounds in tcp_zerocopy_receive net/ipv4/tcp.c:1807
[inline]
BUG: KASAN: slab-out-of-bounds in do_tcp_getsockopt.isra.0+0x2c6c/0x3120
net/ipv4/tcp.c:3654
Read of size 4 at addr ffff8880943cf188 by task syz-executor.2/17508
CPU: 0 PID: 17508 Comm: syz-executor.2 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google
01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
__kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
kasan_report+0x12/0x17 mm/kasan/common.c:618
__asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:131
tcp_zerocopy_receive net/ipv4/tcp.c:1807 [inline]
do_tcp_getsockopt.isra.0+0x2c6c/0x3120 net/ipv4/tcp.c:3654
tcp_getsockopt+0xbf/0xe0 net/ipv4/tcp.c:3680
sock_common_getsockopt+0x94/0xd0 net/core/sock.c:3098
__sys_getsockopt+0x16d/0x310 net/socket.c:2129
__do_sys_getsockopt net/socket.c:2144 [inline]
__se_sys_getsockopt net/socket.c:2141 [inline]
__x64_sys_getsockopt+0xbe/0x150 net/socket.c:2141
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
Fixes: d8e18a516f8f ("net: Use skb accessors in network core")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Acked-by: Soheil Hassas Yeganeh <soh...@google.com>
Cc: Matthew Wilcox (Oracle) <wi...@infradead.org>
Reported-by: syzbot <syzkal...@googlegroups.com>
---
net/ipv4/tcp.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index
79c325a07ba5dc7cfad0a846d1f03bf1787f840b..f98a1882e537dca0102e829cb349be50302d83ab
100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1798,13 +1798,11 @@ static int tcp_zerocopy_receive(struct sock *sk,
}
if (skb_frag_size(frags) != PAGE_SIZE || skb_frag_off(frags)) {
int remaining = zc->recv_skip_hint;
- int size = skb_frag_size(frags);
- while (remaining && (size != PAGE_SIZE ||
+ while (remaining && (skb_frag_size(frags) != PAGE_SIZE
||
skb_frag_off(frags))) {
- remaining -= size;
+ remaining -= skb_frag_size(frags);
frags++;
- size = skb_frag_size(frags);
}
zc->recv_skip_hint -= remaining;
break;
--
2.23.0.581.g78d2f28ef7-goog
