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mm: ensure get_unmapped_area() returns higher address than mmap_min_addr 

This patch fixes the problem that get_unmapped_area() can return illegal
address and result in failing mmap(2) etc.

In case that the address higher than PAGE_SIZE is set to
/proc/sys/vm/mmap_min_addr, the address lower than mmap_min_addr can be
returned by get_unmapped_area(), even if you do not pass any virtual
address hint (i.e.  the second argument).

This is because the current get_unmapped_area() code does not take into
account mmap_min_addr.

This leads to two actual problems as follows:

1. mmap(2) can fail with EPERM on the process without CAP_SYS_RAWIO,
   although any illegal parameter is not passed.

2. The bottom-up search path after the top-down search might not work in
   arch_get_unmapped_area_topdown().

Note: The first and third chunk of my patch, which changes "len" check,
are for more precise check using mmap_min_addr, and not for solving the
above problem.

[How to reproduce]

	--- test.c -------------------------------------------------
	#include <stdio.h>
	#include <unistd.h>
	#include <sys/mman.h>
	#include <sys/errno.h>

	int main(int argc, char *argv[])
	{
		void *ret = NULL, *last_map;
		size_t pagesize = sysconf(_SC_PAGESIZE);

		do {
			last_map = ret;
			ret = mmap(0, pagesize, PROT_NONE,
				MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
	//		printf("ret=%p\n", ret);
		} while (ret != MAP_FAILED);

		if (errno != ENOMEM) {
			printf("ERR: unexpected errno: %d (last map=%p)\n",
			errno, last_map);
		}

		return 0;
	}
	---------------------------------------------------------------

	$ gcc -m32 -o test test.c
	$ sudo sysctl -w vm.mmap_min_addr=65536
	vm.mmap_min_addr = 65536
	$ ./test  (run as non-priviledge user)
	ERR: unexpected errno: 1 (last map=0x10000)

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
wifi-calibration
Akira Takeuchi 2013-11-12 15:08:21 -08:00 committed by Linus Torvalds
parent 0cbef29a78
commit 2afc745f3e
1 changed files with 5 additions and 5 deletions
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10
mm/mmap.c
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@ -1856,7 +1856,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
struct vm_area_struct *vma;
struct vm_unmapped_area_info info;
if (len > TASK_SIZE)
if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
@ -1865,7 +1865,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (TASK_SIZE - len >= addr &&
if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vma->vm_start))
return addr;
}
@ -1895,7 +1895,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
struct vm_unmapped_area_info info;
/* requested length too big for entire address space */
if (len > TASK_SIZE)
if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
@ -1905,14 +1905,14 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (TASK_SIZE - len >= addr &&
if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vma->vm_start))
return addr;
}
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = PAGE_SIZE;
info.low_limit = max(PAGE_SIZE, mmap_min_addr);
info.high_limit = mm->mmap_base;
info.align_mask = 0;
addr = vm_unmapped_area(&info);