Messages in this thread | | | From | "Eric W. Biederman" <> | Date | Tue, 21 Jun 2022 09:30:57 -0500 | Subject | Re: [syzbot] memory leak in setup_mq_sysctls |
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Alexey Gladkov <gladkov.alexey@gmail.com> writes:
> On Sun, Jun 19, 2022 at 11:52:25PM -0700, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 979086f5e006 Merge tag 'fs.fixes.v5.19-rc3' of git://git.k.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=1284331bf00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=c696a83383a77f81 >> dashboard link: https://syzkaller.appspot.com/bug?extid=b4b0d1b35442afbf6fd2 >> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=163e740ff00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=132b758bf00000 >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+b4b0d1b35442afbf6fd2@syzkaller.appspotmail.com > > I'm working on a fix that will remove this memory allocation entirely.
Hmm. The memory should be freed when the corresponding namespace exits. I see retire_mq_sysctls is being called to free this memory. Alex do you see any leaks when you read that code?
So it looks like either someone broke this in linux-next or there is a bug in the memory leak detector, or something truly strange like a memory stop is going on.
I don't see any changes to the ipc subdirectory since v5.19-rc1 in commit 979086f5e006 ("Merge tag 'fs.fixes.v5.19-rc3' of git://git.k.." ) so the idea that the code is broken in linux-next is out.
Which leaves the memory leak detector having trouble with this, or something like a memory stomp is causing problems.
Catalin is it possible that the clever use of ctl_table_arg to hold the reference to the table before it is freed is confusing the memory leak detector? The idiom is old enough I don't expect so, but I have seen bugs lurk for a long time.
Which leaves just a memory stomp or something even stranger in the code. syzkaller can you reproduce this on Linus's branch?
Eric
>> executing program >> BUG: memory leak >> unreferenced object 0xffff888112fc9200 (size 512): >> comm "syz-executor237", pid 3648, jiffies 4294970469 (age 12.270s) >> hex dump (first 32 bytes): >> ef d3 60 85 ff ff ff ff 0c 9b d2 12 81 88 ff ff ..`............. >> 04 00 00 00 a4 01 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace: >> [<ffffffff814b6eb3>] kmemdup+0x23/0x50 mm/util.c:129 >> [<ffffffff82219a9b>] kmemdup include/linux/fortify-string.h:456 [inline] >> [<ffffffff82219a9b>] setup_mq_sysctls+0x4b/0x1c0 ipc/mq_sysctl.c:89 >> [<ffffffff822197f2>] create_ipc_ns ipc/namespace.c:63 [inline] >> [<ffffffff822197f2>] copy_ipcs+0x292/0x390 ipc/namespace.c:91 >> [<ffffffff8127de7c>] create_new_namespaces+0xdc/0x4f0 kernel/nsproxy.c:90 >> [<ffffffff8127e89b>] unshare_nsproxy_namespaces+0x9b/0x120 kernel/nsproxy.c:226 >> [<ffffffff8123f92e>] ksys_unshare+0x2fe/0x600 kernel/fork.c:3165 >> [<ffffffff8123fc42>] __do_sys_unshare kernel/fork.c:3236 [inline] >> [<ffffffff8123fc42>] __se_sys_unshare kernel/fork.c:3234 [inline] >> [<ffffffff8123fc42>] __x64_sys_unshare+0x12/0x20 kernel/fork.c:3234 >> [<ffffffff845aab45>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> [<ffffffff845aab45>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 >> [<ffffffff8460006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 >> >> BUG: memory leak >> unreferenced object 0xffff888112fd5f00 (size 256): >> comm "syz-executor237", pid 3648, jiffies 4294970469 (age 12.270s) >> hex dump (first 32 bytes): >> 00 92 fc 12 81 88 ff ff 00 00 00 00 01 00 00 00 ................ >> 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace: >> [<ffffffff816fea1b>] kmalloc include/linux/slab.h:605 [inline] >> [<ffffffff816fea1b>] kzalloc include/linux/slab.h:733 [inline] >> [<ffffffff816fea1b>] __register_sysctl_table+0x7b/0x7f0 fs/proc/proc_sysctl.c:1344 >> [<ffffffff82219b7a>] setup_mq_sysctls+0x12a/0x1c0 ipc/mq_sysctl.c:112 >> [<ffffffff822197f2>] create_ipc_ns ipc/namespace.c:63 [inline] >> [<ffffffff822197f2>] copy_ipcs+0x292/0x390 ipc/namespace.c:91 >> [<ffffffff8127de7c>] create_new_namespaces+0xdc/0x4f0 kernel/nsproxy.c:90 >> [<ffffffff8127e89b>] unshare_nsproxy_namespaces+0x9b/0x120 kernel/nsproxy.c:226 >> [<ffffffff8123f92e>] ksys_unshare+0x2fe/0x600 kernel/fork.c:3165 >> [<ffffffff8123fc42>] __do_sys_unshare kernel/fork.c:3236 [inline] >> [<ffffffff8123fc42>] __se_sys_unshare kernel/fork.c:3234 [inline] >> [<ffffffff8123fc42>] __x64_sys_unshare+0x12/0x20 kernel/fork.c:3234 >> [<ffffffff845aab45>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> [<ffffffff845aab45>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 >> [<ffffffff8460006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 >> >> BUG: memory leak >> unreferenced object 0xffff888112fbba00 (size 256): >> comm "syz-executor237", pid 3648, jiffies 4294970469 (age 12.270s) >> hex dump (first 32 bytes): >> 78 ba fb 12 81 88 ff ff 00 00 00 00 01 00 00 00 x............... >> 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace: >> [<ffffffff816fef49>] kmalloc include/linux/slab.h:605 [inline] >> [<ffffffff816fef49>] kzalloc include/linux/slab.h:733 [inline] >> [<ffffffff816fef49>] new_dir fs/proc/proc_sysctl.c:978 [inline] >> [<ffffffff816fef49>] get_subdir fs/proc/proc_sysctl.c:1022 [inline] >> [<ffffffff816fef49>] __register_sysctl_table+0x5a9/0x7f0 fs/proc/proc_sysctl.c:1373 >> [<ffffffff82219b7a>] setup_mq_sysctls+0x12a/0x1c0 ipc/mq_sysctl.c:112 >> [<ffffffff822197f2>] create_ipc_ns ipc/namespace.c:63 [inline] >> [<ffffffff822197f2>] copy_ipcs+0x292/0x390 ipc/namespace.c:91 >> [<ffffffff8127de7c>] create_new_namespaces+0xdc/0x4f0 kernel/nsproxy.c:90 >> [<ffffffff8127e89b>] unshare_nsproxy_namespaces+0x9b/0x120 kernel/nsproxy.c:226 >> [<ffffffff8123f92e>] ksys_unshare+0x2fe/0x600 kernel/fork.c:3165 >> [<ffffffff8123fc42>] __do_sys_unshare kernel/fork.c:3236 [inline] >> [<ffffffff8123fc42>] __se_sys_unshare kernel/fork.c:3234 [inline] >> [<ffffffff8123fc42>] __x64_sys_unshare+0x12/0x20 kernel/fork.c:3234 >> [<ffffffff845aab45>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> [<ffffffff845aab45>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 >> [<ffffffff8460006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 >> >> BUG: memory leak >> unreferenced object 0xffff888112fbb900 (size 256): >> comm "syz-executor237", pid 3648, jiffies 4294970469 (age 12.270s) >> hex dump (first 32 bytes): >> 78 b9 fb 12 81 88 ff ff 00 00 00 00 01 00 00 00 x............... >> 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace: >> [<ffffffff816fef49>] kmalloc include/linux/slab.h:605 [inline] >> [<ffffffff816fef49>] kzalloc include/linux/slab.h:733 [inline] >> [<ffffffff816fef49>] new_dir fs/proc/proc_sysctl.c:978 [inline] >> [<ffffffff816fef49>] get_subdir fs/proc/proc_sysctl.c:1022 [inline] >> [<ffffffff816fef49>] __register_sysctl_table+0x5a9/0x7f0 fs/proc/proc_sysctl.c:1373 >> [<ffffffff82219b7a>] setup_mq_sysctls+0x12a/0x1c0 ipc/mq_sysctl.c:112 >> [<ffffffff822197f2>] create_ipc_ns ipc/namespace.c:63 [inline] >> [<ffffffff822197f2>] copy_ipcs+0x292/0x390 ipc/namespace.c:91 >> [<ffffffff8127de7c>] create_new_namespaces+0xdc/0x4f0 kernel/nsproxy.c:90 >> [<ffffffff8127e89b>] unshare_nsproxy_namespaces+0x9b/0x120 kernel/nsproxy.c:226 >> [<ffffffff8123f92e>] ksys_unshare+0x2fe/0x600 kernel/fork.c:3165 >> [<ffffffff8123fc42>] __do_sys_unshare kernel/fork.c:3236 [inline] >> [<ffffffff8123fc42>] __se_sys_unshare kernel/fork.c:3234 [inline] >> [<ffffffff8123fc42>] __x64_sys_unshare+0x12/0x20 kernel/fork.c:3234 >> [<ffffffff845aab45>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] >> [<ffffffff845aab45>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 >> [<ffffffff8460006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 >> >> >> >> --- >> 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 syzkaller@googlegroups.com. >> >> syzbot will keep track of this issue. See: >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot. >> syzbot can test patches for this issue, for details see: >> https://goo.gl/tpsmEJ#testing-patches >>
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