Messages in this thread Patch in this message | | | Date | Thu, 29 Jun 2017 16:02:56 -0700 | From | Jörn Engel <> | Subject | [PATCH] mm: Fix overflow check in expand_upwards() |
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I believe the overflow check was correct, then got subtly broken by commit bd726c90b6b8 Author: Helge Deller <deller@gmx.de> Date: Mon Jun 19 17:34:05 2017 +0200
Allow stack to grow up to address space limit
The old overflow check may have been a bit subtle and I suppose Helge missed its importance.
if (!address) return -ENOMEM;
Functionally the my check is identical to the old one. I just hope the alternative form (and comment!) make it harder to miss and break things in a future patch.
Signed-off-by: Joern Engel <joern@logfs.org> --- mm/mmap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/mmap.c b/mm/mmap.c index a5e3dcd75e79..7366f62c31f4 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2232,7 +2232,8 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) /* Guard against exceeding limits of the address space. */ address &= PAGE_MASK; - if (address >= TASK_SIZE) + /* second check is for integer overflow */ + if (address >= TASK_SIZE || address + PAGE_SIZE < address) return -ENOMEM; address += PAGE_SIZE; -- 2.1.4
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