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linux-user/mmap.c: Avoid choosing NULL as start address

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mmap() is required by the linux kernel ABI and POSIX to return a
non-NULL address when the implementation chooses a start address for the
mapping.

The current implementation of mmap_find_vma_reserved() can return NULL
as start address of a mapping which leads to subsequent crashes inside
the guests glibc, e.g. output of qemu-arm-static --strace executing a
test binary stx_test:

    1879 mmap2(NULL,8388608,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS|0x20000,-1,0) = 0x00000000
    1879 write(2,0xf6fd39d0,79) stx_test: allocatestack.c:514: allocate_stack: Assertion `mem != NULL' failed.

This patch fixes mmap_find_vma_reserved() by skipping NULL as start
address while searching for a suitable mapping start address.

CC: Riku Voipio <riku.voipio@iki.fi>
CC: Laurent Vivier <laurent@vivier.eu>
CC: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Maximilian Riemensberger <riemensberger@cadami.net>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <1515286904-86418-1-git-send-email-riemensberger@cadami.net>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Maximilian Riemensberger 2018-01-07 01:01:44 +00:00 committed by Laurent Vivier
parent 10fa993aae
commit 95e6d4305a
1 changed files with 1 additions and 1 deletions
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linux-user/mmap.c
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@ -234,7 +234,7 @@ static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size)
if (prot) {
end_addr = addr;
}
if (addr + size == end_addr) {
if (addr && addr + size == end_addr) {
break;
}
addr -= qemu_host_page_size;