Yes, you are absolutely correct. I can reproduce this now, when
kernel.core_pattern is set to "|".
I can also confirm that the first kernel that this is broken in is 5.3,
as it works fine in 5.2 and below.
I will look into this and hopefully get this fixed for you. Thanks for
reporting!
Engineering Notes:
RIP: 0010:do_coredump+0x536/0xb30
$ eu-addr2line do_coredump+0x536 -e vmlinux-5.3.0-29-generic
/build/linux-OZAq_R/linux-5.3.0/include/linux/fs.h:2841:7
This is the function file_start_write():
2839 static inline void file_start_write(struct file *file)
2840 {
2841 if (!S_ISREG(file_inode(file)->i_mode))
2842 return;
2843 __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, true);
2844 }
This is called from do_coredump():
565 void do_coredump(const kernel_siginfo_t *siginfo)
566 {
...
788 if (!dump_interrupted()) {
789 file_start_write(cprm.file);
790 core_dumped = binfmt->core_dump(&cprm);
791 file_end_write(cprm.file);
792 }
...
810 }
On kernels 5.2 and before, kernel.core_pattern=| normally outputs:
[ 39.328638] Core dump to | pipe failed
This is output is from the pipe section of do_coredump():
565 void do_coredump(const kernel_siginfo_t *siginfo)
566 {
...
623 ispipe = format_corename(&cn, &cprm, &argv, &argc);
624
625 if (ispipe) {
...
681 sub_info = call_usermodehelper_setup(helper_argv[0],
682 helper_argv, NULL, GFP_KERNEL,
683 umh_pipe_setup, NULL, &cprm);
684 if (sub_info)
685 retval = call_usermodehelper_exec(sub_info,
686 UMH_WAIT_EXEC);
687
688 kfree(helper_argv);
689 if (retval) {
690 printk(KERN_INFO "Core dump to |%s pipe failed\n",
691 cn.corename);
692 goto close_fail;
693 }
...
810 }
With kernel.core_pattern=|, format_corename() still interprets this as
the pipe path with:
191 static int format_corename(struct core_name *cn, struct coredump_params
*cprm,
192 size_t **argv, int *argc)
193 {
...
196 int ispipe = (*pat_ptr == '|');
...
335 return ispipe;
336 }
Which checks the first byte of the core_pattern string to see if it is a
"|".
This means we really want the call to call_usermodehelper_exec() in
do_coredump() to fail, so we take the if(retval) step and output "Core
dump to |%s pipe failed\n".
Note that cn.corename is NULL when kernel.core_pattern=|.
For some reason with 5.3 and later, this call to
call_usermodehelper_exec() is not failing, and execution continues on
and breaks at file_start_write(cprm.file); at the end of do_coredump().
call_usermodehelper_exec() calls umh_pipe_setup() and creates the pipe
used. Something has likely changed in the pipe subsystem.
I will update when I figure out what.
** Also affects: linux (Ubuntu Eoan)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Focal)
Importance: Undecided
Status: Confirmed
** Changed in: linux (Ubuntu Eoan)
Status: New => Confirmed
** Changed in: linux (Ubuntu Eoan)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Focal)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Eoan)
Assignee: (unassigned) => Matthew Ruffell (mruffell)
** Changed in: linux (Ubuntu Focal)
Assignee: (unassigned) => Matthew Ruffell (mruffell)
** Description changed:
If process that listens socket on any port crashes (segmentation fault) it
becomes unkillable.
Kill command does not kill this process.
Port that listen crashed process never be freed.
journalctl shows error:
Feb 13 13:28:09 vbun04 kernel: socktest[1359]: segfault at 21 ip
000055ec3a6bf11e sp 00007ffd88899fb0 error 6 in socktest[55ec3a6bf000+1000]
Feb 13 13:28:09 vbun04 kernel: Code: 04 24 02 00 17 70 89 c5 48 b8 30 30 30
30 30 30 30 30 89 ef 48 89 44 24 08 e8 8e ff ff ff be 0a 00 00 00 89 ef e8 72
ff ff ff <c7> 04 25 21 00 00 00 21 00 00 00 48 8b 44 24 18
Feb 13 13:28:09 vbun04 kernel: BUG: kernel NULL pointer dereference, address:
0000000000000020
Feb 13 13:28:09 vbun04 kernel: #PF: supervisor read access in kernel mode
Feb 13 13:28:09 vbun04 kernel: #PF: error_code(0x0000) - not-present page
Feb 13 13:28:09 vbun04 kernel: PGD 0 P4D 0
Feb 13 13:28:09 vbun04 kernel: Oops: 0000 [#1] SMP NOPTI
Feb 13 13:28:09 vbun04 kernel: CPU: 1 PID: 1359 Comm: socktest Tainted: G
OE 5.3.0-29-generic #31-Ubuntu
Feb 13 13:28:09 vbun04 kernel: Hardware name: innotek GmbH
VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
Feb 13 13:28:09 vbun04 kernel: RIP: 0010:do_coredump+0x536/0xb30
Feb 13 13:28:09 vbun04 kernel: Code: 00 48 8b bd 18 ff ff ff 48 85 ff 74 05
e8 c2 47 fa ff 65 48 8b 04 25 c0 6b 01 00 48 8b 00 48 8b 7d a0 a8 04 0f 85 65
05 00 00 <48> 8b 57 20 0f b7 02 66 25 00 f0 66 3d 00 80 0f
Feb 13 13:28:09 vbun04 kernel: RSP: 0000:ffffb464c2c5fca8 EFLAGS: 00010246
Feb 13 13:28:09 vbun04 kernel: RAX: 0000000000000000 RBX: ffff9d4b76995100
RCX: 0000000000001afc
Feb 13 13:28:09 vbun04 kernel: RDX: 0000000000000000 RSI: ffffb464c2c5fc68
RDI: 0000000000000000
Feb 13 13:28:09 vbun04 kernel: RBP: ffffb464c2c5fdd8 R08: 0000000000000400
R09: ffffb464c2c5fbe0
Feb 13 13:28:09 vbun04 kernel: R10: ffff9d4b75d01170 R11: 0000000000000000
R12: ffff9d4b7b3df540
Feb 13 13:28:09 vbun04 kernel: R13: 0000000000000001 R14: 0000000000000000
R15: ffffffffb9f15920
Feb 13 13:28:09 vbun04 kernel: FS: 00007f6c91911540(0000)
GS:ffff9d4b7db00000(0000) knlGS:0000000000000000
Feb 13 13:28:09 vbun04 kernel: CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
Feb 13 13:28:09 vbun04 kernel: CR2: 0000000000000020 CR3: 00000000723ac003
CR4: 00000000000606e0
Feb 13 13:28:09 vbun04 kernel: Call Trace:
Feb 13 13:28:09 vbun04 kernel: ? wake_up_state+0x10/0x20
Feb 13 13:28:09 vbun04 kernel: ? __send_signal+0x1eb/0x3f0
Feb 13 13:28:09 vbun04 kernel: get_signal+0x159/0x880
Feb 13 13:28:09 vbun04 kernel: do_signal+0x34/0x280
Feb 13 13:28:09 vbun04 kernel: ? bad_area+0x47/0x50
Feb 13 13:28:09 vbun04 kernel: exit_to_usermode_loop+0xbf/0x160
Feb 13 13:28:09 vbun04 kernel: prepare_exit_to_usermode+0x77/0xa0
Feb 13 13:28:09 vbun04 kernel: retint_user+0x8/0x8
Feb 13 13:28:09 vbun04 kernel: RIP: 0033:0x55ec3a6bf11e
Feb 13 13:28:09 vbun04 kernel: Code: 04 24 02 00 17 70 89 c5 48 b8 30 30 30
30 30 30 30 30 89 ef 48 89 44 24 08 e8 8e ff ff ff be 0a 00 00 00 89 ef e8 72
ff ff ff <c7> 04 25 21 00 00 00 21 00 00 00 48 8b 44 24 18
Feb 13 13:28:09 vbun04 kernel: RSP: 002b:00007ffd88899fb0 EFLAGS: 00010217
Feb 13 13:28:09 vbun04 kernel: RAX: 0000000000000000 RBX: 0000000000000000
RCX: 00007f6c918424eb
Feb 13 13:28:09 vbun04 kernel: RDX: 0000000000000010 RSI: 000000000000000a
RDI: 0000000000000003
Feb 13 13:28:09 vbun04 kernel: RBP: 0000000000000003 R08: 0000000000000000
R09: 00007f6c919331f0
Feb 13 13:28:09 vbun04 kernel: R10: 0000000000000000 R11: 0000000000000217
R12: 000055ec3a6bf150
Feb 13 13:28:09 vbun04 kernel: R13: 00007ffd8889a0b0 R14: 0000000000000000
R15: 0000000000000000
Feb 13 13:28:09 vbun04 kernel: Modules linked in: vboxsf(OE) nls_utf8 isofs
vboxvideo(OE) intel_rapl_msr intel_rapl_common crct10dif_pclmul vmwgfx
crc32_pclmul ghash_clmulni_intel aesni_intel ttm drm_kms_helper a
Feb 13 13:28:09 vbun04 kernel: CR2: 0000000000000020
Feb 13 13:28:09 vbun04 kernel: ---[ end trace 278d665c8727286a ]---
Feb 13 13:28:09 vbun04 kernel: RIP: 0010:do_coredump+0x536/0xb30
Feb 13 13:28:09 vbun04 kernel: Code: 00 48 8b bd 18 ff ff ff 48 85 ff 74 05
e8 c2 47 fa ff 65 48 8b 04 25 c0 6b 01 00 48 8b 00 48 8b 7d a0 a8 04 0f 85 65
05 00 00 <48> 8b 57 20 0f b7 02 66 25 00 f0 66 3d 00 80 0f
Feb 13 13:28:09 vbun04 kernel: RSP: 0000:ffffb464c2c5fca8 EFLAGS: 00010246
Feb 13 13:28:09 vbun04 kernel: RAX: 0000000000000000 RBX: ffff9d4b76995100
RCX: 0000000000001afc
Feb 13 13:28:09 vbun04 kernel: RDX: 0000000000000000 RSI: ffffb464c2c5fc68
RDI: 0000000000000000
Feb 13 13:28:09 vbun04 kernel: RBP: ffffb464c2c5fdd8 R08: 0000000000000400
R09: ffffb464c2c5fbe0
Feb 13 13:28:09 vbun04 kernel: R10: ffff9d4b75d01170 R11: 0000000000000000
R12: ffff9d4b7b3df540
Feb 13 13:28:09 vbun04 kernel: R13: 0000000000000001 R14: 0000000000000000
R15: ffffffffb9f15920
Feb 13 13:28:09 vbun04 kernel: FS: 00007f6c91911540(0000)
GS:ffff9d4b7db00000(0000) knlGS:0000000000000000
Feb 13 13:28:09 vbun04 kernel: CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
Feb 13 13:28:09 vbun04 kernel: CR2: 0000000000000020 CR3: 00000000723ac003
CR4: 00000000000606e0
+ Steps to Reproduce:
+ Set kernel.core_pattern sysctl to "|" to disable coredumps.
- Steps to Reproduce:
+ $ sudo sysctl kernel.core_pattern="|"
Compile and run following code:
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
int main()
{
- int listenfd = 0;
- struct sockaddr_in serv_addr;
+ int listenfd = 0;
+ struct sockaddr_in serv_addr;
- listenfd = socket(AF_INET, SOCK_STREAM, 0);
- memset(&serv_addr, '0', sizeof(serv_addr));
+ listenfd = socket(AF_INET, SOCK_STREAM, 0);
+ memset(&serv_addr, '0', sizeof(serv_addr));
- serv_addr.sin_family = AF_INET;
- serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
- serv_addr.sin_port = htons(6000);
+ serv_addr.sin_family = AF_INET;
+ serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+ serv_addr.sin_port = htons(6000);
- bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
+ bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
- listen(listenfd, 10);
+ listen(listenfd, 10);
- *(int*)33 = 33;
+ *(int*)33 = 33;
- return 0;
+ return 0;
}
Process segfaulted and becomes unkillable, opened socket ports busy.
ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: linux-image-generic 5.3.0.29.33
ProcVersionSignature: Ubuntu 5.3.0-29.31-generic 5.3.13
Uname: Linux 5.3.0-29-generic x86_64
AlsaDevices:
- total 0
- crw-rw----+ 1 root audio 116, 1 фев 13 13:24 seq
- crw-rw----+ 1 root audio 116, 33 фев 13 13:24 timer
+ total 0
+ crw-rw----+ 1 root audio 116, 1 фев 13 13:24 seq
+ crw-rw----+ 1 root audio 116, 33 фев 13 13:24 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord':
'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
'/dev/snd/timer'] failed with exit code 1:
CurrentDesktop: KDE
Date: Thu Feb 13 13:49:19 2020
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lsusb: Error: [Errno 2] No such file or directory: 'lsusb': 'lsusb'
MachineType: innotek GmbH VirtualBox
PciMultimedia:
-
+
ProcFB: 0 svgadrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.3.0-29-generic
root=UUID=cd3a004e-4e27-4c93-8ae6-e1942680f565 ro mitigations=off
ipv6.disable=1 net.ifnames=0 video=1280x960
RelatedPackageVersions:
- linux-restricted-modules-5.3.0-29-generic N/A
- linux-backports-modules-5.3.0-29-generic N/A
- linux-firmware 1.183.3
+ linux-restricted-modules-5.3.0-29-generic N/A
+ linux-backports-modules-5.3.0-29-generic N/A
+ linux-firmware 1.183.3
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
WifiSyslog:
-
+
dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias:
dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
dmi.product.family: Virtual Machine
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH
** Tags added: seg
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https://bugs.launchpad.net/bugs/1863086
Title:
unkillable process (kernel NULL pointer dereference)
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