Public bug reported:
Intially found when running snapd integration test suite on Arch on
5.2.x kernels. The problem was reproduced on daily eoan cloud images
with kernel Ubuntu 5.3.0-10.11-generic 5.3.0-rc8 (as reported in
/proc/version_signature)
Stracing trivial Go binary results in a deadlock when both strace and
the binary being traced end up in D state.
Example code:
```
package main
import (
"os"
"syscall"
)
func main() {
syscall.Exec("/bin/echo", []string{"/bin/echo", "Hello"}, os.Environ())
}
```
$ go build exec.go
$ while true; do echo '- go'; strace -f -e 'execve' ./exec 2>/dev/null ; done
..
Hello
- go
Hello
- go
Hello
- go
^C
At which point strace does not react to ^C. This can only be unlocked by
issuing SIGKILL to either strace or the binary being traced.
Process list:
PID TTY STAT TIME COMMAND
808 ? Ss 0:00 sshd: guest [priv]
1003 ? S 0:01 \_ sshd: guest@pts/0,pts/1,pts/2
1038 pts/0 Ss 0:00 \_ -bash
23473 pts/0 D+ 0:00 | \_ strace -f -e execve ./exec
23476 pts/0 Dl+ 0:00 | \_ ./exec
The dump of blocked kernel tasks:
[ 414.886023] sysrq: Show Blocked State
[ 414.886695] task PC stack pid father
[ 414.886739] strace D 0 23473 1038 0x00000000
[ 414.886741] Call Trace:
[ 414.886747] __schedule+0x2b9/0x6c0
[ 414.886748] schedule+0x42/0xb0
[ 414.886750] schedule_preempt_disabled+0xe/0x10
[ 414.886751] __mutex_lock.isra.0+0x182/0x4f0
[ 414.886752] __mutex_lock_killable_slowpath+0x13/0x20
[ 414.886754] mutex_lock_killable+0x2e/0x40
[ 414.886756] mm_access+0x27/0xa0
[ 414.886758] process_vm_rw_core.isra.0+0x10f/0x590
[ 414.886760] ? __switch_to_asm+0x40/0x70
[ 414.886761] ? __switch_to_asm+0x34/0x70
[ 414.886762] ? __switch_to_asm+0x34/0x70
[ 414.886763] ? __switch_to_asm+0x40/0x70
[ 414.886764] ? reschedule_interrupt+0xa/0x20
[ 414.886767] ? __check_object_size+0x4d/0x150
[ 414.886770] ? _copy_from_user+0x3e/0x60
[ 414.886772] ? rw_copy_check_uvector+0x62/0x110
[ 414.886774] ? __check_object_size+0x4d/0x150
[ 414.886774] ? _copy_from_user+0x3e/0x60
[ 414.886776] process_vm_rw+0x106/0x130
[ 414.886778] ? common_file_perm+0x5e/0x110
[ 414.886780] ? vfs_write+0x173/0x1a0
[ 414.886781] ? ksys_write+0x67/0xe0
[ 414.886782] __x64_sys_process_vm_readv+0x2b/0x30
[ 414.886785] do_syscall_64+0x5a/0x130
[ 414.886786] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 414.886788] RIP: 0033:0x7fa7b90ec19e
[ 414.886794] Code: Bad RIP value.
[ 414.886794] RSP: 002b:00007ffc293ab9f8 EFLAGS: 00000246 ORIG_RAX:
0000000000000136
[ 414.886796] RAX: ffffffffffffffda RBX: 00007ffc293aba90 RCX: 00007fa7b90ec19e
[ 414.886796] RDX: 0000000000000001 RSI: 00007ffc293aba00 RDI: 0000000000005bb5
[ 414.886797] RBP: 000000c00008a010 R08: 0000000000000001 R09: 0000000000000000
[ 414.886797] R10: 00007ffc293aba10 R11: 0000000000000246 R12: 0000000000001000
[ 414.886797] R13: 0000000000001000 R14: 0000000000005bb5 R15: 0000000000000000
[ 414.886799] exec D 0 23476 23473 0x80004003
[ 414.886800] Call Trace:
[ 414.886802] __schedule+0x2b9/0x6c0
[ 414.886803] schedule+0x42/0xb0
[ 414.886805] de_thread+0x1c3/0x480
[ 414.886806] flush_old_exec+0x2a/0x260
[ 414.886808] ? load_elf_phdrs+0x70/0xb0
[ 414.886809] load_elf_binary+0x344/0x11e0
[ 414.886810] ? get_user_pages_remote+0x146/0x230
[ 414.886811] ? get_acl+0x1d/0x120
[ 414.886813] ? ima_bprm_check+0x87/0xb0
[ 414.886814] search_binary_handler+0x8b/0x1c0
[ 414.886816] __do_execve_file.isra.0+0x4fe/0x860
[ 414.886817] __x64_sys_execve+0x39/0x50
[ 414.886818] do_syscall_64+0x5a/0x130
[ 414.886820] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 414.886820] RIP: 0033:0x459ffb
[ 414.886821] Code: Bad RIP value.
[ 414.886822] RSP: 002b:000000c000082e40 EFLAGS: 00000206 ORIG_RAX:
000000000000003b
[ 414.886822] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000459ffb
[ 414.886823] RDX: 000000c000098000 RSI: 000000c000096000 RDI: 000000c00008a010
[ 414.886823] RBP: 000000c000082ed0 R08: 0000000000000000 R09: 0000000000000000
[ 414.886824] R10: 0000000000000000 R11: 0000000000000206 R12: 000000c00009a848
[ 414.886824] R13: 000000000000085b R14: 000000c00009a848 R15: 000000c0000980b0
A patch was proposed on LKML back in 2016
https://lore.kernel.org/patchwork/patch/719314/ but it was not accepted
into mainline.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Incomplete
** Attachment added: "version.log"
https://bugs.launchpad.net/bugs/1845180/+attachment/5290926/+files/version.log
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https://bugs.launchpad.net/bugs/1845180
Title:
strace deadlock when tracing a trivial Go program
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