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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
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

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

@ -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