Messages in this thread Patch in this message | | | Date | Tue, 19 Dec 2023 19:15:31 +0000 | Subject | Re: [linus:master] [x86/entry] be5341eb0d: WARNING:CPU:#PID:#at_int80_emulation | From | Andrew Cooper <> |
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On 19/12/2023 6:20 pm, Linus Torvalds wrote: > On Tue, 19 Dec 2023 at 01:58, Borislav Petkov <bp@alien8.de> wrote: >> Looking at the dmesg, I think you missed the most important part - the >> preceding line: >> >> [ 13.480504][ T48] CFI failure at int80_emulation+0x67/0xb0 (target: sys_ni_posix_timers+0x0/0x70; expected type: 0xb02b34d9) >> ^^^^^^^^^^^ > So I think the issue here is that sys_ni_posix_timers is just linker > alias that is used for any non-implemented posix timer system call.
My reading of the original report is that there used to be:
dmesg.WARNING:CPU:#PID:#at_do_int80_syscall_32
and now there's:
dmesg.WARNING:CPU:#PID:#at_int80_emulation
i.e. kCFI was broken before, and all we did with be5341eb0d43 was change the inlining, and therefore how the error was rendered.
> See: > > #define __SYS_NI(abi, name) \ > SYSCALL_ALIAS(__##abi##_##name, sys_ni_posix_timers);
AFAICT, this is the problem, but it was preexiting too.
This is stuffing a function of type void into an array of function pointers wanting pt_regs * which is indeed a kCFI violation.
Isn't the fix simply this?
~Andrew
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index fd9d12de7e92..12195164d5a4 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -1171,7 +1171,7 @@ asmlinkage long sys_ni_syscall(void); #endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */ -asmlinkage long sys_ni_posix_timers(void); +asmlinkage long sys_ni_posix_timers(const struct pt_regs *regs); /* * Kernel code should not call syscalls (i.e., sys_xyzyyz()) directly. diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c index 828aeecbd1e8..29692354a908 100644 --- a/kernel/time/posix-stubs.c +++ b/kernel/time/posix-stubs.c @@ -22,7 +22,7 @@ #include <asm/syscall_wrapper.h> #endif -asmlinkage long sys_ni_posix_timers(void) +asmlinkage long sys_ni_posix_timers(const struct pt_regs *regs) { pr_err_once("process %d (%s) attempted a POSIX timer syscall " "while CONFIG_POSIX_TIMERS is not set\n",
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