From: H.J. Lu Date: Fri, 2 Dec 2022 00:36:02 +0000 (-0800) Subject: x86-64 strncpy: Properly handle the length parameter [BZ# 29839] X-Git-Tag: glibc-2.37~128 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e5672763c44f16ddbc42809f5def7c6a962602bd;p=thirdparty%2Fglibc.git 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 --- diff --git a/sysdeps/x86_64/multiarch/strncpy-avx2.S b/sysdeps/x86_64/multiarch/strncpy-avx2.S index e9afd8fbed1..3e6350ce4aa 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 49eaf4cbd96..dec8cccc2be 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