[syzbot] [net?] general protection fault in phy_start_cable_test_tdr

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f9db28bb09f4 Merge branch 'net-redundant-judgments'
git tree: net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1656cc7b980000
kernel config: https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf270e2069645b6bd2c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1582047b980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=100af825980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/585e02f7fe7b/disk-f9db28bb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b9faf5d24900/vmlinux-f9db28bb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f9df5868ea4f/bzImage-f9db28bb.xz

The issue was bisected to:

commit 3688ff3077d3f334cee1d4b61d8bfb6a9508c2d2
Author: Maxime Chevallier <maxime.c...@bootlin.com>
Date: Wed Aug 21 15:10:05 2024 +0000

net: ethtool: cable-test: Target the command to the requested PHY

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10163b05980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12163b05980000
console output: https://syzkaller.appspot.com/x/log.txt?x=14163b05980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5cf270...@syzkaller.appspotmail.com
Fixes: 3688ff3077d3 ("net: ethtool: cable-test: Target the command to the requested PHY")

Oops: general protection fault, probably for non-canonical address 0xdffffc00000000f8: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000007c0-0x00000000000007c7]
CPU: 0 UID: 0 PID: 5234 Comm: syz-executor293 Not tainted 6.11.0-rc4-syzkaller-00565-gf9db28bb09f4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
RIP: 0010:phy_start_cable_test_tdr+0x3a/0x5c0 drivers/net/phy/phy.c:885
Code: ec 38 48 89 54 24 18 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df e8 e4 24 2b fb 48 8d bb c0 07 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 05 e8 9a 66 92 fb 48 8b 83 c0 07 00 00 48 89 44
RSP: 0018:ffffc90003c7f230 EFLAGS: 00010202
RAX: 00000000000000f8 RBX: 0000000000000000 RCX: ffff888029b23c00
RDX: 0000000000000000 RSI: ffffc90003c7f740 RDI: 00000000000007c0
RBP: ffffc90003c7f470 R08: ffffffff89cb116d R09: 1ffff1100452bc15
R10: dffffc0000000000 R11: ffffffff86686630 R12: ffffc90003c7f3f0
R13: dffffc0000000000 R14: ffffc90003c7f740 R15: 0000000000000000
FS: 000055555a907380(0000) GS:ffff8880b9200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055fce9c1f000 CR3: 000000001a7d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ethnl_act_cable_test_tdr+0x607/0x10d0 net/ethtool/cabletest.c:350
genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0xb14/0xec0 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0x221/0x270 net/socket.c:745
____sys_sendmsg+0x525/0x7d0 net/socket.c:2597
___sys_sendmsg net/socket.c:2651 [inline]
__sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3311b2ef49
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 01 1a 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe6e4b3118 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f3311b2ef49
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe6e4b3170
R13: 00007f3311b7c406 R14: 0000000000000003 R15: 00007ffe6e4b3150
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:phy_start_cable_test_tdr+0x3a/0x5c0 drivers/net/phy/phy.c:885
Code: ec 38 48 89 54 24 18 49 89 f6 48 89 fb 49 bd 00 00 00 00 00 fc ff df e8 e4 24 2b fb 48 8d bb c0 07 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 05 e8 9a 66 92 fb 48 8b 83 c0 07 00 00 48 89 44
RSP: 0018:ffffc90003c7f230 EFLAGS: 00010202
RAX: 00000000000000f8 RBX: 0000000000000000 RCX: ffff888029b23c00
RDX: 0000000000000000 RSI: ffffc90003c7f740 RDI: 00000000000007c0
RBP: ffffc90003c7f470 R08: ffffffff89cb116d R09: 1ffff1100452bc15
R10: dffffc0000000000 R11: ffffffff86686630 R12: ffffc90003c7f3f0
R13: dffffc0000000000 R14: ffffc90003c7f740 R15: 0000000000000000
FS: 000055555a907380(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3311b15a00 CR3: 000000001a7d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: ec in (%dx),%al
1: 38 48 89 cmp %cl,-0x77(%rax)
4: 54 push %rsp
5: 24 18 and $0x18,%al
7: 49 89 f6 mov %rsi,%r14
a: 48 89 fb mov %rdi,%rbx
d: 49 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%r13
14: fc ff df
17: e8 e4 24 2b fb call 0xfb2b2500
1c: 48 8d bb c0 07 00 00 lea 0x7c0(%rbx),%rdi
23: 48 89 f8 mov %rdi,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 05 je 0x36
31: e8 9a 66 92 fb call 0xfb9266d0
36: 48 8b 83 c0 07 00 00 mov 0x7c0(%rbx),%rax
3d: 48 rex.W
3e: 89 .byte 0x89
3f: 44 rex.R


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Edward Adam Davis]

There is a logical error in checking phydev

#syz test: net-next main

diff --git a/net/ethtool/cabletest.c b/net/ethtool/cabletest.c
index 3a91b65c1f9a..2fe5951b8e45 100644
--- a/net/ethtool/cabletest.c
+++ b/net/ethtool/cabletest.c
@@ -342,7 +342,7 @@ int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info)
phydev = ethnl_req_get_phydev(&req_info,
tb[ETHTOOL_A_CABLE_TEST_TDR_HEADER],
info->extack);
- if (!IS_ERR_OR_NULL(phydev)) {
+ if (IS_ERR_OR_NULL(phydev)) {
ret = -EOPNOTSUPP;
goto out_dev_put;
}

[Diogo Jahchan Koike]

#syz test

In ethnl_act_cable_test_tdr, phydev is tested for the condition of being
null or an error by checking IS_ERR_OR_NULL, however the result is being
negated and lets a null phydev go through. Simply removing the logical
NOT on the conditional suffices.
---
net/ethtool/cabletest.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethtool/cabletest.c b/net/ethtool/cabletest.c
index d365ad5f5434..f25da884b3dd 100644
--- a/net/ethtool/cabletest.c
+++ b/net/ethtool/cabletest.c
@@ -346,7 +346,7 @@ int ethnl_act_cable_test_tdr(struct sk_buff *skb, struct genl_info *info)

phydev = ethnl_req_get_phydev(&req_info,
tb[ETHTOOL_A_CABLE_TEST_TDR_HEADER],
info->extack);
- if (!IS_ERR_OR_NULL(phydev)) {
+ if (IS_ERR_OR_NULL(phydev)) {
ret = -EOPNOTSUPP;
goto out_dev_put;
}

--
2.43.0

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: lock held when returning to user space in ethnl_act_cable_test_tdr

================================================
WARNING: lock held when returning to user space!
6.11.0-rc4-syzkaller-00681-ge5899b60f52a-dirty #0 Not tainted
------------------------------------------------
syz.0.15/6073 is leaving the kernel with locks still held!
1 lock held by syz.0.15/6073:
#0: ffffffff8fc84c08 (rtnl_mutex){+.+.}-{3:3}, at: ethnl_act_cable_test_tdr+0x3d2/0x10c0 net/ethtool/cabletest.c:341


Tested on:

commit: e5899b60 Merge branch '100GbE' of git://git.kernel.org..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17c0c7a7980000

kernel config: https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf270e2069645b6bd2c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16325a43980000

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: lock held when returning to user space in ethnl_act_cable_test_tdr

================================================
WARNING: lock held when returning to user space!
6.11.0-rc4-syzkaller-00681-ge5899b60f52a-dirty #0 Not tainted
------------------------------------------------

syz.0.15/6086 is leaving the kernel with locks still held!
1 lock held by syz.0.15/6086:

#0: ffffffff8fc84c08 (rtnl_mutex){+.+.}-{3:3}, at: ethnl_act_cable_test_tdr+0x3d2/0x10c0 net/ethtool/cabletest.c:341


Tested on:

commit: e5899b60 Merge branch '100GbE' of git://git.kernel.org..
git tree: net-next

console output: https://syzkaller.appspot.com/x/log.txt?x=16a5267b980000

kernel config: https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf270e2069645b6bd2c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=17c1c57b980000

[Maxime Chevallier]

Hi,

On Tue, 27 Aug 2024 17:09:22 -0700
syzbot <syzbot+5cf270...@syzkaller.appspotmail.com> wrote:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: f9db28bb09f4 Merge branch 'net-redundant-judgments'
> git tree: net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1656cc7b980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
> dashboard link: https://syzkaller.appspot.com/bug?extid=5cf270e2069645b6bd2c
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1582047b980000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=100af825980000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/585e02f7fe7b/disk-f9db28bb.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b9faf5d24900/vmlinux-f9db28bb.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/f9df5868ea4f/bzImage-f9db28bb.xz
>
> The issue was bisected to:
>
> commit 3688ff3077d3f334cee1d4b61d8bfb6a9508c2d2
> Author: Maxime Chevallier <maxime.c...@bootlin.com>
> Date: Wed Aug 21 15:10:05 2024 +0000
>
> net: ethtool: cable-test: Target the command to the requested PHY

A fix for this has been sent already :

https://lore.kernel.org/netdev/20240827092314.250028...@bootlin.com/

Thanks,

Maxime

[syzbot]

syzbot suspects this issue was fixed by commit:

commit ad78337cb20c1a52781a7b329b1a747d91be3491
Author: Maxime Chevallier <maxime.c...@bootlin.com>
Date: Tue Aug 27 09:23:13 2024 +0000

net: ethtool: cable-test: Release RTNL when the PHY isn't found

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17bee307980000
start commit: f9db28bb09f4 Merge branch 'net-redundant-judgments'
git tree: net-next

kernel config: https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf270e2069645b6bd2c

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10542a33980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=178c6225980000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: net: ethtool: cable-test: Release RTNL when the PHY isn't found

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.