From: NRK <nrk@disroot.org>
To: musl@lists.openwall.com
Subject: [musl] [PATCH] fix undefined behavior from large shifts
Date: Sat, 4 Jun 2022 23:25:50 +0600 [thread overview]
Message-ID: <20220604172550.uf7vboamzar4etk3@gen2.localdomain> (raw)
int maybe 16bits in which case shifting left by 16 is UB.
cast to uint32_t before doing the shift to avoid such issues.
---
src/string/memmem.c | 8 ++++----
src/string/strstr.c | 8 ++++----
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/src/string/memmem.c b/src/string/memmem.c
index 11eff86e..4d19a922 100644
--- a/src/string/memmem.c
+++ b/src/string/memmem.c
@@ -12,8 +12,8 @@ static char *twobyte_memmem(const unsigned char *h, size_t k, const unsigned cha
static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
{
- uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8;
- uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8;
+ uint32_t nw = (uint32_t)n[0]<<24 | (uint32_t)n[1]<<16 | n[2]<<8;
+ uint32_t hw = (uint32_t)h[0]<<24 | (uint32_t)h[1]<<16 | h[2]<<8;
for (h+=3, k-=3; k; k--, hw = (hw|*h++)<<8)
if (hw == nw) return (char *)h-3;
return hw == nw ? (char *)h-3 : 0;
@@ -21,8 +21,8 @@ static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned c
static char *fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
{
- uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
- uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
+ uint32_t nw = (uint32_t)n[0]<<24 | (uint32_t)n[1]<<16 | n[2]<<8 | n[3];
+ uint32_t hw = (uint32_t)h[0]<<24 | (uint32_t)h[1]<<16 | h[2]<<8 | h[3];
for (h+=4, k-=4; k; k--, hw = hw<<8 | *h++)
if (hw == nw) return (char *)h-4;
return hw == nw ? (char *)h-4 : 0;
diff --git a/src/string/strstr.c b/src/string/strstr.c
index 96657bc2..a68c1adb 100644
--- a/src/string/strstr.c
+++ b/src/string/strstr.c
@@ -10,16 +10,16 @@ static char *twobyte_strstr(const unsigned char *h, const unsigned char *n)
static char *threebyte_strstr(const unsigned char *h, const unsigned char *n)
{
- uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8;
- uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8;
+ uint32_t nw = (uint32_t)n[0]<<24 | (uint32_t)n[1]<<16 | n[2]<<8;
+ uint32_t hw = (uint32_t)h[0]<<24 | (uint32_t)h[1]<<16 | h[2]<<8;
for (h+=2; *h && hw != nw; hw = (hw|*++h)<<8);
return *h ? (char *)h-2 : 0;
}
static char *fourbyte_strstr(const unsigned char *h, const unsigned char *n)
{
- uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
- uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
+ uint32_t nw = (uint32_t)n[0]<<24 | (uint32_t)n[1]<<16 | n[2]<<8 | n[3];
+ uint32_t hw = (uint32_t)h[0]<<24 | (uint32_t)h[1]<<16 | h[2]<<8 | h[3];
for (h+=3; *h && hw != nw; hw = hw<<8 | *++h);
return *h ? (char *)h-3 : 0;
}
--
2.35.1
next reply other threads:[~2022-06-04 17:26 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-04 17:25 NRK [this message]
2022-06-04 18:04 ` Pascal Cuoq
2022-06-04 18:16 ` Rich Felker
2022-06-04 18:55 ` NRK
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