From: Vineet Gupta Date: Fri, 23 Apr 2021 19:16:25 +0000 (-0700) Subject: ARC: entry: fix off-by-one error in syscall number validation X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3433adc8bd09fc9f29b8baddf33b4ecd1ecd2cdc;p=linux.git ARC: entry: fix off-by-one error in syscall number validation We have NR_syscall syscalls from [0 .. NR_syscall-1]. However the check for invalid syscall number is "> NR_syscall" as opposed to >=. This off-by-one error erronesously allows "NR_syscall" to be treated as valid syscall causeing out-of-bounds access into syscall-call table ensuing a crash (holes within syscall table have a invalid-entry handler but this is beyond the array implementing the table). This problem showed up on v5.6 kernel when testing glibc 2.33 (v5.10 kernel capable, includng faccessat2 syscall 439). The v5.6 kernel has NR_syscalls=439 (0 to 438). Due to the bug, 439 passed by glibc was not handled as -ENOSYS but processed leading to a crash. Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/48 Reported-by: Shahab Vahedi Cc: Signed-off-by: Vineet Gupta --- diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 1743506081da6..2cb8dfe866b66 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -177,7 +177,7 @@ tracesys: ; Do the Sys Call as we normally would. ; Validate the Sys Call number - cmp r8, NR_syscalls + cmp r8, NR_syscalls - 1 mov.hi r0, -ENOSYS bhi tracesys_exit @@ -255,7 +255,7 @@ ENTRY(EV_Trap) ;============ Normal syscall case ; syscall num shd not exceed the total system calls avail - cmp r8, NR_syscalls + cmp r8, NR_syscalls - 1 mov.hi r0, -ENOSYS bhi .Lret_from_system_call