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* [glibc] x86-64 strncpy: Properly handle the length parameter [BZ# 29839]
@ 2022-12-02 16:19 H.J. Lu
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From: H.J. Lu @ 2022-12-02 16:19 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e5672763c44f16ddbc42809f5def7c6a962602bd
commit e5672763c44f16ddbc42809f5def7c6a962602bd
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Thu Dec 1 16:36:02 2022 -0800
x86-64 strncpy: Properly handle the length parameter [BZ# 29839]
On x32, the size_t parameter may be passed in the lower 32 bits of a
64-bit register with the non-zero upper 32 bits. The string/memory
functions written in assembly can only use the lower 32 bits of a
64-bit register as length or must clear the upper 32 bits before using
the full 64-bit register for length.
This pach fixes strncpy for x32. Tested on x86-64 and x32. On x86-64,
libc.so is the same with and without the fix.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
Diff:
---
sysdeps/x86_64/multiarch/strncpy-avx2.S | 4 ++++
sysdeps/x86_64/multiarch/strncpy-evex.S | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/sysdeps/x86_64/multiarch/strncpy-avx2.S b/sysdeps/x86_64/multiarch/strncpy-avx2.S
index e9afd8fbed..3e6350ce4a 100644
--- a/sysdeps/x86_64/multiarch/strncpy-avx2.S
+++ b/sysdeps/x86_64/multiarch/strncpy-avx2.S
@@ -52,6 +52,10 @@
.section SECTION(.text), "ax", @progbits
ENTRY(STRNCPY)
+# ifdef __ILP32__
+ /* Clear the upper 32 bits. */
+ movl %edx, %edx
+# endif
/* Filter zero length strings and very long strings. Zero
length strings just return, very long strings are handled by
just running rep stos{b|l} to zero set (which will almost
diff --git a/sysdeps/x86_64/multiarch/strncpy-evex.S b/sysdeps/x86_64/multiarch/strncpy-evex.S
index 49eaf4cbd9..dec8cccc2b 100644
--- a/sysdeps/x86_64/multiarch/strncpy-evex.S
+++ b/sysdeps/x86_64/multiarch/strncpy-evex.S
@@ -80,6 +80,10 @@
.section SECTION(.text), "ax", @progbits
ENTRY(STRNCPY)
+# ifdef __ILP32__
+ /* Clear the upper 32 bits. */
+ movl %edx, %edx
+# endif
/* Filter zero length strings and very long strings. Zero
length strings just return, very long strings are handled by
just running rep stos{b|l} to zero set (which will almost
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