From e5672763c44f16ddbc42809f5def7c6a962602bd Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Thu, 1 Dec 2022 16:36:02 -0800 Subject: 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 --- sysdeps/x86_64/multiarch/strncpy-avx2.S | 4 ++++ sysdeps/x86_64/multiarch/strncpy-evex.S | 4 ++++ 2 files changed, 8 insertions(+) (limited to 'sysdeps') 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 -- cgit v1.2.3