Messages in this thread Patch in this message | | | Date | Mon, 30 Oct 2017 21:44:35 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH v3 0/12] arm+arm64: vdso unification to lib/vdso/ |
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On Mon, Oct 30, 2017 at 01:34:13PM -0700, Mark Salyzyn wrote: > On 10/30/2017 07:18 AM, Mark Rutland wrote: > > On Fri, Oct 27, 2017 at 03:23:48PM -0700, Mark Salyzyn wrote: > > > Note I noticed a bug in the old implementation of __kernel_clock_getres; > > > it was checking only the lower 32bits of the pointer; this would work > > > for most cases but could fail in a few. > > Sorry if this is a stupid question, but do you mean from a prior version > > of this series, or the one in the kernel today? > > apinski@cavium.com noticed this as part of the existing upstream arm64 > assembler when he did the original conversion to C.
Just to check, does the below address the issue, or is there something that I've missed?
Thanks, Mark.
---->8---- From 3557ca259f0a6dbb35a057256552545ec0cef677 Mon Sep 17 00:00:00 2001 From: Mark Rutland <mark.rutland@arm.com> Date: Mon, 30 Oct 2017 21:23:19 +0000 Subject: [PATCH] arm64: vdso: fix clock_getres for 4GiB-aligned res
The vdso tries to check for a NULL res pointer in __kernel_clock_getres, but only checks the lower 32 bits as is uses CBZ on the W register the res pointer is held in.
Thus, if the res pointer happened to be aligned to a 4GiB boundary, we'd spuriously skip storing the timespec to it, while returning a zero error code to the caller.
Prevent this by checking the whole pointer, using CBZ on the X register the res pointer is held in.
Fixes: 9031fefde6f2ac1d ("arm64: VDSO support") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reported-by: Andrew Pinski <apinski@cavium.com> Reported-by: Mark Salyzyn <salyzyn@android.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm64/kernel/vdso/gettimeofday.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S index 76320e920965..c39872a7b03c 100644 --- a/arch/arm64/kernel/vdso/gettimeofday.S +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -309,7 +309,7 @@ ENTRY(__kernel_clock_getres) b.ne 4f ldr x2, 6f 2: - cbz w1, 3f + cbz x1, 3f stp xzr, x2, [x1] 3: /* res == NULL. */ -- 2.11.0
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