This is a note to let you know that I've just added the patch titled reboot: fix overflow parsing reboot cpu number to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: reboot-fix-overflow-parsing-reboot-cpu-number.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From df5b0ab3e08a156701b537809914b339b0daa526 Mon Sep 17 00:00:00 2001 From: Matteo Croce <mcroce@xxxxxxxxxxxxx> Date: Fri, 13 Nov 2020 22:52:07 -0800 Subject: reboot: fix overflow parsing reboot cpu number From: Matteo Croce <mcroce@xxxxxxxxxxxxx> commit df5b0ab3e08a156701b537809914b339b0daa526 upstream. 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 do_syscall_64+0x2d/0x40 Fixes: 1b3a5d02ee07 ("reboot: move arch/x86 reboot= handling to generic kernel") Signed-off-by: Matteo Croce <mcroce@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Fabian Frederick <fabf@xxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Guenter Roeck <linux@xxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxx> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Cc: Petr Mladek <pmladek@xxxxxxxx> Cc: Robin Holt <robinmholt@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20201103214025.116799-3-mcroce@xxxxxxxxxxxxxxxxxxx Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> [sudip: use reboot_mode instead of mode] Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/reboot.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -519,6 +519,13 @@ static int __init reboot_setup(char *str reboot_cpu = simple_strtoul(str+3, NULL, 0); else reboot_mode = REBOOT_SOFT; + if (reboot_cpu >= num_possible_cpus()) { + pr_err("Ignoring the CPU number in reboot= option. " + "CPU %d exceeds possible cpu number %d\n", + reboot_cpu, num_possible_cpus()); + reboot_cpu = 0; + break; + } break; case 'g': Patches currently in stable-queue which might be from mcroce@xxxxxxxxxxxxx are queue-4.14/reboot-fix-overflow-parsing-reboot-cpu-number.patch queue-4.14/revert-kernel-reboot.c-convert-simple_strtoul-to-kstrtoint.patch