From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57890) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eXzMC-0005Qu-Ql for qemu-devel@nongnu.org; Sat, 06 Jan 2018 20:02:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eXzM8-0004CO-Sv for qemu-devel@nongnu.org; Sat, 06 Jan 2018 20:02:36 -0500 Received: from dd7730.kasserver.com ([85.13.132.46]:54003) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eXzM8-0004B3-LY for qemu-devel@nongnu.org; Sat, 06 Jan 2018 20:02:32 -0500 From: Maximilian Riemensberger Date: Sun, 7 Jan 2018 01:01:44 +0000 Message-Id: <1515286904-86418-1-git-send-email-riemensberger@cadami.net> Subject: [Qemu-devel] [PATCH v2] linux-user/mmap.c: Avoid choosing NULL as start address List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel Cc: Maximilian Riemensberger , Riku Voipio , Laurent Vivier , Peter Maydell 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 CC: Laurent Vivier CC: Peter Maydell Signed-off-by: Maximilian Riemensberger --- Changes since v1: - Applied feedback from Laurent Vivier linux-user/mmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 4888f53..0fbfd6d 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -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; -- 2.7.4