We have NR_syscall syscalls from [0 .. NR_syscall-1]. However the check for invalid syscall number is "> NR_syscall". This off-by-one error erronesously allows "NR_syscall" itself as valid and when passed causes out-of-bounds syscall-call table access leading to crash.
This problem showed up when testing glibc 2.33 (v5.10 kernel capable, includng faccessat2 syscall (439) against a v5.6 kernel with NR_syscalls=439 (0 to 438). Due to the bug, 439 was not returned with -ENOSYS but processed leading to a crash. Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/48 Reported-by: Shahab Vahedi <sha...@synopsys.com> Signed-off-by: Vineet Gupta <vgu...@synopsys.com> --- arch/arc/kernel/entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 1743506081da..aea9b558993d 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -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 -- 2.25.1 _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
