Re: [PATCH] arm64: Mitigate MTE issues with str{n}cmp()
From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-09-21 13:25:41
On Fri, Sep 17, 2021 at 03:59:30PM +0100, Robin Murphy wrote:
quoted hunk ↗ jump to hunk
As with strlen(), the patches importing the updated str{n}cmp() implementations were originally developed and tested before the advent of CONFIG_KASAN_HW_TAGS, and have subsequently revealed not to be MTE-safe. Since in-kernel MTE is still a rather niche case, let it temporarily fall back to the generic C versions for correctness until we can figure out the best fix. Reported-by: Branislav Rankov <redacted> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- arch/arm64/include/asm/assembler.h | 5 +++++ arch/arm64/include/asm/string.h | 2 ++ arch/arm64/lib/strcmp.S | 2 +- arch/arm64/lib/strncmp.S | 2 +- 4 files changed, 9 insertions(+), 2 deletions(-)diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 89faca0e740d..bfa58409a4d4 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h@@ -525,6 +525,11 @@ alternative_endif #define EXPORT_SYMBOL_NOKASAN(name) EXPORT_SYMBOL(name) #endif +#ifdef CONFIG_KASAN_HW_TAGS +#define EXPORT_SYMBOL_NOHWKASAN(name) +#else +#define EXPORT_SYMBOL_NOHWKASAN(name) EXPORT_SYMBOL_NOKASAN(name) +#endif
I think that depending on how we solve this in future, we might want to have: * EXPORT_SYMBOL_NOSWKASAN for generic/sw-tags (this would be a rename of the existing EXPORT_SYMBOL_NOKASAN) * EXPORT_SYMBOL_NOHWKASAN for hw tags * EXPORT_SYMBOL_NOKASAN for generic/sw-tags/hw-tags ... so then it's a bit clearer what's handled in each case. Regardless, for now this is certainly good enough. FWIW: Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks, Mark.
quoted hunk ↗ jump to hunk
/* * Emit a 64-bit absolute little endian symbol reference in a way that * ensures that it will be resolved at build time, even when building adiff --git a/arch/arm64/include/asm/string.h b/arch/arm64/include/asm/string.h index 3a3264ff47b9..95f7686b728d 100644 --- a/arch/arm64/include/asm/string.h +++ b/arch/arm64/include/asm/string.h@@ -12,11 +12,13 @@ extern char *strrchr(const char *, int c); #define __HAVE_ARCH_STRCHR extern char *strchr(const char *, int c); +#ifndef CONFIG_KASAN_HW_TAGS #define __HAVE_ARCH_STRCMP extern int strcmp(const char *, const char *); #define __HAVE_ARCH_STRNCMP extern int strncmp(const char *, const char *, __kernel_size_t); +#endif #define __HAVE_ARCH_STRLEN extern __kernel_size_t strlen(const char *);diff --git a/arch/arm64/lib/strcmp.S b/arch/arm64/lib/strcmp.S index d7bee210a798..83bcad72ec97 100644 --- a/arch/arm64/lib/strcmp.S +++ b/arch/arm64/lib/strcmp.S@@ -173,4 +173,4 @@ L(done): ret SYM_FUNC_END_PI(strcmp) -EXPORT_SYMBOL_NOKASAN(strcmp) +EXPORT_SYMBOL_NOHWKASAN(strcmp)diff --git a/arch/arm64/lib/strncmp.S b/arch/arm64/lib/strncmp.S index 48d44f7fddb1..e42bcfcd37e6 100644 --- a/arch/arm64/lib/strncmp.S +++ b/arch/arm64/lib/strncmp.S@@ -258,4 +258,4 @@ L(ret0): ret SYM_FUNC_END_PI(strncmp) -EXPORT_SYMBOL_NOKASAN(strncmp) +EXPORT_SYMBOL_NOHWKASAN(strncmp)-- 2.21.0.dirty
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