3.5.7.29 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Akira Takeuchi <takeuchi.akr@xxxxxxxxxxxxxxxx>
commit 2afc745f3e3079ab16c826be4860da2529054dd2 upstream.
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@xxxxxxxxxxxxxxxx>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@xxxxxxxxxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
As we do not have vm_unmapped_area(), make arch_get_unmapped_area_topdown()
calculate the lower limit for the new area's end address and then compare
addresses with this instead of with len. In the process, fix an off-by-one
error which could result in returning 0 if mm->mmap_base == len.]
Signed-off-by: Akira Takeuchi <takeuchi.akr@xxxxxxxxxxxxxxxx>
[akira: Backported to 3.5:
Based on Ben's backport for 3.2-stable kernel. ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
mm/mmap.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 7e24763..529f72c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1443,7 +1443,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
struct vm_area_struct *vma;
unsigned long start_addr;
- if (len > TASK_SIZE)
+ if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
@@ -1452,7 +1452,7 @@ 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;
}
@@ -1515,9 +1515,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr = addr0, start_addr;
+ unsigned long low_limit = max(PAGE_SIZE, mmap_min_addr);
/* 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)
@@ -1527,7 +1528,7 @@ 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;
}
@@ -1542,7 +1543,7 @@ try_again:
/* either no address requested or can't fit in requested address hole */
start_addr = addr = mm->free_area_cache;
- if (addr < len)
+ if (addr < low_limit + len)
goto fail;
addr -= len;
@@ -1563,7 +1564,7 @@ try_again:
/* try just below the current vma->vm_start */
addr = vma->vm_start-len;
- } while (len < vma->vm_start);
+ } while (vma->vm_start >= low_limit + len);
fail:
/*
--
1.8.3.2
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