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Message-Id: <20201014212746.161363-1-mcroce@linux.microsoft.com>
Date: Wed, 14 Oct 2020 23:27:46 +0200
From: Matteo Croce <mcroce@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org
Cc: Guenter Roeck <linux@...ck-us.net>, Petr Mladek <pmladek@...e.com>,
Arnd Bergmann <arnd@...db.de>, Mike Rapoport <rppt@...nel.org>,
Kees Cook <keescook@...omium.org>,
Pavel Tatashin <pasha.tatashin@...een.com>,
Robin Holt <robinmholt@...il.com>,
Fabian Frederick <fabf@...net.be>, stable@...r.kernel.org
Subject: [PATCH] reboot: fix parsing of reboot cpu number
From: Matteo Croce <mcroce@...rosoft.com>
The kernel cmdline reboot= argument allows to specify the CPU used
for rebooting, with the syntax `s####` among the other flags, e.g.
reboot=soft,s4
reboot=warm,s31,force
In the early days the parsing was done with simple_strtoul(), later
deprecated in favor of the safer kstrtoint() which handles overflow.
But kstrtoint() returns -EINVAL if there are non-digit characters
in a string, so if this flag is not the last given, it's silently
ignored as well as the subsequent ones.
To fix it, use _parse_integer() which still handles overflow, but
restores the old behaviour of parsing until a non-digit character
is found.
While at it, limit the CPU number to num_possible_cpus(),
because setting it to a value lower than INT_MAX but higher
than NR_CPUS produces the following error on reboot and shutdown:
BUG: unable to handle page fault for address: ffffffff90ab1bb0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 1c09067 P4D 1c09067 PUD 1c0a063 PMD 0
Oops: 0000 [#1] SMP
CPU: 1 PID: 1 Comm: systemd-shutdow Not tainted 5.9.0-rc8-kvm #110
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
RIP: 0010:migrate_to_reboot_cpu+0xe/0x60
Code: ea ea 00 48 89 fa 48 c7 c7 30 57 f1 81 e9 fa ef ff ff 66 2e 0f 1f 84 00 00 00 00 00 53 8b 1d d5 ea ea 00 e8 14 33 fe ff 89 da <48> 0f a3 15 ea fc bd 00 48 89 d0 73 29 89 c2 c1 e8 06 65 48 8b 3c
RSP: 0018:ffffc90000013e08 EFLAGS: 00010246
RAX: ffff88801f0a0000 RBX: 0000000077359400 RCX: 0000000000000000
RDX: 0000000077359400 RSI: 0000000000000002 RDI: ffffffff81c199e0
RBP: ffffffff81c1e3c0 R08: ffff88801f41f000 R09: ffffffff81c1e348
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 00007f32bedf8830 R14: 00000000fee1dead R15: 0000000000000000
FS: 00007f32bedf8980(0000) GS:ffff88801f480000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff90ab1bb0 CR3: 000000001d057000 CR4: 00000000000006a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__do_sys_reboot.cold+0x34/0x5b
? vfs_writev+0x92/0xc0
? do_writev+0x52/0xd0
do_syscall_64+0x2d/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f32bfaaecd3
Code: 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 89 fa be 69 19 12 28 bf ad de e1 fe b8 a9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 89 81 0c 00 f7 d8
RSP: 002b:00007fff6265fb58 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f32bfaaecd3
RDX: 0000000001234567 RSI: 0000000028121969 RDI: 00000000fee1dead
RBP: 0000000000000000 R08: 0000000000008020 R09: 00007fff6265ef60
R10: 00007f32bedf8830 R11: 0000000000000202 R12: 0000000000000000
R13: 0000557bba2c51c0 R14: 0000000000000000 R15: 00007fff6265fbc8
CR2: ffffffff90ab1bb0
---[ end trace b813e80157136563 ]---
RIP: 0010:migrate_to_reboot_cpu+0xe/0x60
Code: ea ea 00 48 89 fa 48 c7 c7 30 57 f1 81 e9 fa ef ff ff 66 2e 0f 1f 84 00 00 00 00 00 53 8b 1d d5 ea ea 00 e8 14 33 fe ff 89 da <48> 0f a3 15 ea fc bd 00 48 89 d0 73 29 89 c2 c1 e8 06 65 48 8b 3c
RSP: 0018:ffffc90000013e08 EFLAGS: 00010246
RAX: ffff88801f0a0000 RBX: 0000000077359400 RCX: 0000000000000000
RDX: 0000000077359400 RSI: 0000000000000002 RDI: ffffffff81c199e0
RBP: ffffffff81c1e3c0 R08: ffff88801f41f000 R09: ffffffff81c1e348
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 00007f32bedf8830 R14: 00000000fee1dead R15: 0000000000000000
FS: 00007f32bedf8980(0000) GS:ffff88801f480000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff90ab1bb0 CR3: 000000001d057000 CR4: 00000000000006a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009
Kernel Offset: disabled
---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]---
Fixes: 1b3a5d02ee07 ("reboot: move arch/x86 reboot= handling to generic kernel")
Fixes: 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint")
Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
---
kernel/reboot.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/kernel/reboot.c b/kernel/reboot.c
index e7b78d5ae1ab..79e5d4522d0e 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -18,6 +18,8 @@
#include <linux/syscore_ops.h>
#include <linux/uaccess.h>
+#include "../lib/kstrtox.h"
+
/*
* this indicates whether you can reboot with ctrl-alt-del: the default is yes
*/
@@ -552,19 +554,23 @@ static int __init reboot_setup(char *str)
case 's':
{
- int rc;
-
- if (isdigit(*(str+1))) {
- rc = kstrtoint(str+1, 0, &reboot_cpu);
- if (rc)
- return rc;
- } else if (str[1] == 'm' && str[2] == 'p' &&
- isdigit(*(str+3))) {
- rc = kstrtoint(str+3, 0, &reboot_cpu);
- if (rc)
- return rc;
- } else
+ unsigned long long number;
+ unsigned int rc;
+
+ /*
+ * reboot_cpu is s[mp]#### with #### being the processor
+ * to be used for rebooting. Skip 's' or 'smp' prefix.
+ */
+ str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;
+
+ if (isdigit(str[0])) {
+ rc = _parse_integer(str, 10, &number);
+ if (rc & KSTRTOX_OVERFLOW || number > num_possible_cpus())
+ return -ERANGE;
+ reboot_cpu = number;
+ } else {
*mode = REBOOT_SOFT;
+ }
break;
}
case 'g':
--
2.26.2
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