From 19c22f3a29fa8669c477f20a65f6c7c27108972a Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Tue, 6 Oct 2015 13:35:10 -0400 Subject: [PATCH 1/3] word-at-a-time.h: fix some Kbuild files arch/tile added word-at-a-time.h after the patch that added generic-y entries; the generic-y entry is now stale. arch/h8300 is newer than the generic-y patch for word-at-a-time.h, and needs a generic-y entry. arch/powerpc seems to have gotten a generic-y entry by mistake in the first patch; this change removes it. Signed-off-by: Chris Metcalf --- arch/h8300/include/asm/Kbuild | 1 + arch/powerpc/include/asm/Kbuild | 1 - arch/tile/include/asm/Kbuild | 1 - 3 files changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/h8300/include/asm/Kbuild b/arch/h8300/include/asm/Kbuild index 70e6ae1e7006..373cb23301e3 100644 --- a/arch/h8300/include/asm/Kbuild +++ b/arch/h8300/include/asm/Kbuild @@ -73,4 +73,5 @@ generic-y += uaccess.h generic-y += ucontext.h generic-y += unaligned.h generic-y += vga.h +generic-y += word-at-a-time.h generic-y += xor.h diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild index ac1662956e0c..ab9f4e0ed4cf 100644 --- a/arch/powerpc/include/asm/Kbuild +++ b/arch/powerpc/include/asm/Kbuild @@ -7,4 +7,3 @@ generic-y += mcs_spinlock.h generic-y += preempt.h generic-y += rwsem.h generic-y += vtime.h -generic-y += word-at-a-time.h diff --git a/arch/tile/include/asm/Kbuild b/arch/tile/include/asm/Kbuild index 0b6cacaad933..ba35c41c71ff 100644 --- a/arch/tile/include/asm/Kbuild +++ b/arch/tile/include/asm/Kbuild @@ -40,5 +40,4 @@ generic-y += termbits.h generic-y += termios.h generic-y += trace_clock.h generic-y += types.h -generic-y += word-at-a-time.h generic-y += xor.h From c753bf34c94e5ac901e625e52f47320eeec4de2d Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Tue, 6 Oct 2015 14:20:45 -0400 Subject: [PATCH 2/3] word-at-a-time.h: support zero_bytemask() on alpha and tile Both alpha and tile needed implementations of zero_bytemask. The alpha version is untested. Signed-off-by: Chris Metcalf --- arch/alpha/include/asm/word-at-a-time.h | 2 ++ arch/tile/include/asm/word-at-a-time.h | 8 +++++++- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/alpha/include/asm/word-at-a-time.h b/arch/alpha/include/asm/word-at-a-time.h index 6b340d0f1521..902e6ab00a06 100644 --- a/arch/alpha/include/asm/word-at-a-time.h +++ b/arch/alpha/include/asm/word-at-a-time.h @@ -52,4 +52,6 @@ static inline unsigned long find_zero(unsigned long bits) #endif } +#define zero_bytemask(mask) ((2ul << (find_zero(mask) * 8)) - 1) + #endif /* _ASM_WORD_AT_A_TIME_H */ diff --git a/arch/tile/include/asm/word-at-a-time.h b/arch/tile/include/asm/word-at-a-time.h index 9e5ce0d7b292..b66a693c2c34 100644 --- a/arch/tile/include/asm/word-at-a-time.h +++ b/arch/tile/include/asm/word-at-a-time.h @@ -6,7 +6,7 @@ struct word_at_a_time { /* unused */ }; #define WORD_AT_A_TIME_CONSTANTS {} -/* Generate 0x01 byte values for non-zero bytes using a SIMD instruction. */ +/* Generate 0x01 byte values for zero bytes using a SIMD instruction. */ static inline unsigned long has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c) { @@ -33,4 +33,10 @@ static inline long find_zero(unsigned long mask) #endif } +#ifdef __BIG_ENDIAN +#define zero_bytemask(mask) (~1ul << (63 - __builtin_clzl(mask))) +#else +#define zero_bytemask(mask) ((2ul << __builtin_ctzl(mask)) - 1) +#endif + #endif /* _ASM_WORD_AT_A_TIME_H */ From 990486c8af044f89bddfbde1d1cf9fde449bedbf Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Tue, 6 Oct 2015 12:37:41 -0400 Subject: [PATCH 3/3] strscpy: zero any trailing garbage bytes in the destination It's possible that the destination can be shadowed in userspace (as, for example, the perf buffers are now). So we should take care not to leak data that could be inspected by userspace. Signed-off-by: Chris Metcalf --- lib/string.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/string.c b/lib/string.c index 8dbb7b1eab50..84775ba873b9 100644 --- a/lib/string.c +++ b/lib/string.c @@ -203,12 +203,13 @@ ssize_t strscpy(char *dest, const char *src, size_t count) unsigned long c, data; c = *(unsigned long *)(src+res); - *(unsigned long *)(dest+res) = c; if (has_zero(c, &data, &constants)) { data = prep_zero_mask(c, data, &constants); data = create_zero_mask(data); + *(unsigned long *)(dest+res) = c & zero_bytemask(data); return res + find_zero(data); } + *(unsigned long *)(dest+res) = c; res += sizeof(unsigned long); count -= sizeof(unsigned long); max -= sizeof(unsigned long);