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x86-64 strncpy: Properly handle the length parameter [BZ# 29839]

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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>
This commit is contained in:
H.J. Lu 2022-12-01 16:36:02 -08:00
parent f566b02852
commit e5672763c4
2 changed files with 8 additions and 0 deletions
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4
sysdeps/x86_64/multiarch/strncpy-avx2.S
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@ -52,6 +52,10 @@
.section SECTION(.text), "ax", @progbits .section SECTION(.text), "ax", @progbits
ENTRY(STRNCPY) ENTRY(STRNCPY)
# ifdef __ILP32__
/* Clear the upper 32 bits. */
movl %edx, %edx
# endif
/* Filter zero length strings and very long strings. Zero /* Filter zero length strings and very long strings. Zero
length strings just return, very long strings are handled by length strings just return, very long strings are handled by
just running rep stos{b|l} to zero set (which will almost just running rep stos{b|l} to zero set (which will almost

4
sysdeps/x86_64/multiarch/strncpy-evex.S
View File

@ -80,6 +80,10 @@
.section SECTION(.text), "ax", @progbits .section SECTION(.text), "ax", @progbits
ENTRY(STRNCPY) ENTRY(STRNCPY)
# ifdef __ILP32__
/* Clear the upper 32 bits. */
movl %edx, %edx
# endif
/* Filter zero length strings and very long strings. Zero /* Filter zero length strings and very long strings. Zero
length strings just return, very long strings are handled by length strings just return, very long strings are handled by
just running rep stos{b|l} to zero set (which will almost just running rep stos{b|l} to zero set (which will almost