From: Matteo Croce mcroce@microsoft.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@microsoft.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':