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The reallocarray function is an extension from OpenBSD. It is an
integer-overflow-safe replacement for realloc(p, X*Y) and
malloc(X*Y) (realloc(NULL, X*Y)). It can therefore help in preventing
certain security issues in code.
This is an updated version of a patch originally submitted by Rüdiger
Sonderfeld in May 2014 [1].
Checked on i686-linux-gnu and x86_64-linux-gnu.
[1] <https://sourceware.org/ml/libc-alpha/2014-05/msg00481.html>.
2017-05-30 Dennis Wölfing <denniswoelfing@gmx.de>
Rüdiger Sonderfeld <ruediger@c-plusplus.de>
* include/stdlib.h (__libc_reallocarray): New declaration.
* malloc/Makefile (routines): Add reallocarray.
(tests): Add tst-reallocarray.c.
* malloc/Versions: Add reallocarray and __libc_reallocarray.
* malloc/malloc-internal.h (check_mul_overflow_size_t): New inline
function.
* malloc/malloc.h (reallocarray): New declaration.
* stdlib/stdlib.h (reallocarray): Likewise.
* malloc/reallocarray.c: New file.
* malloc/tst-reallocarray.c: New test file.
* manual/memory.texi: Document reallocarray.
* sysdeps/unix/sysv/linux/aarch64/libc.abilist: Add reallocarray.
* sysdeps/unix/sysv/linux/alpha/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/arm/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/hppa/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/i386/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/ia64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/microblaze/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/nios2/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/sh/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/tilepro/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist: Likewise.
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The dynamic linker currently uses __libc_memalign for TLS-related
allocations. The goal is to switch to malloc instead. If the minimal
malloc follows the ABI fundamental alignment, we can assume that malloc
provides this alignment, and thus skip explicit alignment in a few
cases as an optimization.
It was requested on libc-alpha that MALLOC_ALIGNMENT should be used,
although this results in wasted space if MALLOC_ALIGNMENT is larger
than the fundamental alignment. (The dynamic linker cannot assume
that the non-minimal malloc will provide an alignment of
MALLOC_ALIGNMENT; the ABI provides _Alignof (max_align_t) only.)
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Previously, a thread M invoking fork would acquire locks in this order:
(M1) malloc arena locks (in the registered fork handler)
(M2) libio list lock
A thread F invoking flush (NULL) would acquire locks in this order:
(F1) libio list lock
(F2) individual _IO_FILE locks
A thread G running getdelim would use this order:
(G1) _IO_FILE lock
(G2) malloc arena lock
After executing (M1), (F1), (G1), none of the threads can make progress.
This commit changes the fork lock order to:
(M'1) libio list lock
(M'2) malloc arena locks
It explicitly encodes the lock order in the implementations of fork,
and does not rely on the registration order, thus avoiding the deadlock.
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