commit: 7edc8b0ac16cbaed7cb4ea4c6b95ce98d2997e84
From: Siddhesh Poyarekar <[email protected]>
Date: Tue, 29 May 2012 15:06:22 -0700
Subject: mm/fork: fix overflow in vma length when copying mmap on clone
The vma length in dup_mmap is calculated and stored in a unsigned int,
which is insufficient and hence overflows for very large maps (beyond
16TB). The following program demonstrates this:
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#define GIG 1024 * 1024 * 1024L
#define EXTENT 16393
int main(void)
{
int i, r;
void *m;
char buf[1024];
for (i = 0; i < EXTENT; i++) {
m = mmap(NULL, (size_t) 1 * 1024 * 1024 * 1024L,
PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS,
0, 0);
if (m == (void *)-1)
printf("MMAP Failed: %d\n", m);
else
printf("%d : MMAP returned %p\n", i, m);
r = fork();
if (r == 0) {
printf("%d: successed\n", i);
return 0;
} else if (r < 0)
printf("FORK Failed: %d\n", r);
else if (r > 0)
wait(NULL);
}
return 0;
}
Increase the storage size of the result to unsigned long, which is
sufficient for storing the difference between addresses.
Signed-off-by: Siddhesh Poyarekar <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
kernel/fork.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 5b13eea..017fb23 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -386,7 +386,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct
*oldmm)
}
charge = 0;
if (mpnt->vm_flags & VM_ACCOUNT) {
- unsigned int len = (mpnt->vm_end - mpnt->vm_start) >>
PAGE_SHIFT;
+ unsigned long len;
+ len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
goto fail_nomem;
charge = len;
--
1.7.3.4
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