[PATCH net] sch_red: fix off-by-one checks in red_check_params()

[PATCH net] sch_red: fix off-by-one checks in red_check_params()

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

This fixes following syzbot report:

UBSAN: shift-out-of-bounds in ./include/net/red.h:237:23
shift exponent 32 is too large for 32-bit type 'unsigned int'
CPU: 1 PID: 8418 Comm: syz-executor170 Not tainted 5.12.0-rc4-next-20210324-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:327
 red_set_parms include/net/red.h:237 [inline]
 choke_change.cold+0x3c/0xc8 net/sched/sch_choke.c:414
 qdisc_create+0x475/0x12f0 net/sched/sch_api.c:1247
 tc_modify_qdisc+0x4c8/0x1a50 net/sched/sch_api.c:1663
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5553
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502
 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43f039
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdfa725168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f039
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 0000000000403020 R08: 0000000000400488 R09: 0000000000400488
R10: 0000000000400488 R11: 0000000000000246 R12: 00000000004030b0
R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488

Fixes: 8afa10cbe281 ("net_sched: red: Avoid illegal values")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
 include/net/red.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/red.h b/include/net/red.h
index 0b39eff1d50aebc43784ebec3fe615fec0bf995c..be11dbd26492094e8b477339c66b3a098e06c39f 100644
--- a/include/net/red.h
+++ b/include/net/red.h
@@ -171,9 +171,9 @@ static inline void red_set_vars(struct red_vars *v)
 static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog,
 				    u8 Scell_log, u8 *stab)
 {
-	if (fls(qth_min) + Wlog > 32)
+	if (fls(qth_min) + Wlog >= 32)
 		return false;
-	if (fls(qth_max) + Wlog > 32)
+	if (fls(qth_max) + Wlog >= 32)
 		return false;
 	if (Scell_log >= 32)
 		return false;
-- 
2.31.0.291.g576ba9dcdaf-goog

Re: [PATCH net] sch_red: fix off-by-one checks in red_check_params()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Thu, 25 Mar 2021 11:14:53 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> This fixes following syzbot report:
> 
> UBSAN: shift-out-of-bounds in ./include/net/red.h:237:23
> shift exponent 32 is too large for 32-bit type 'unsigned int'
> CPU: 1 PID: 8418 Comm: syz-executor170 Not tainted 5.12.0-rc4-next-20210324-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
>  __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:327
>  red_set_parms include/net/red.h:237 [inline]
>  choke_change.cold+0x3c/0xc8 net/sched/sch_choke.c:414
>  qdisc_create+0x475/0x12f0 net/sched/sch_api.c:1247
>  tc_modify_qdisc+0x4c8/0x1a50 net/sched/sch_api.c:1663
>  rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5553
>  netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502
>  netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
>  netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
>  netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
>  sock_sendmsg_nosec net/socket.c:654 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:674
>  ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
>  __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x43f039
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffdfa725168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f039
> RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000004
> RBP: 0000000000403020 R08: 0000000000400488 R09: 0000000000400488
> R10: 0000000000400488 R11: 0000000000000246 R12: 00000000004030b0
> R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488
> 
> [...]

Here is the summary with links:
  - [net] sch_red: fix off-by-one checks in red_check_params()
    https://git.kernel.org/netdev/net/c/3a87571f0ffc

You are awesome, thank you!
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