[PATCH 3.10 112/139] mm: fix overflow check in expand_upwards()

From: Willy Tarreau
Date: Wed Nov 01 2017 - 17:28:45 EST


From: Helge Deller <deller@xxxxxx>

commit 37511fb5c91db93d8bd6e3f52f86e5a7ff7cfcdf upstream.

JÃÂrn Engel noticed that the expand_upwards() function might not return
-ENOMEM in case the requested address is (unsigned long)-PAGE_SIZE and
if the architecture didn't defined TASK_SIZE as multiple of PAGE_SIZE.

Affected architectures are arm, frv, m68k, blackfin, h8300 and xtensa
which all define TASK_SIZE as 0xffffffff, but since none of those have
an upwards-growing stack we currently have no actual issue.

Nevertheless let's fix this just in case any of the architectures with
an upward-growing stack (currently parisc, metag and partly ia64) define
TASK_SIZE similar.

Link: http://lkml.kernel.org/r/20170702192452.GA11868@xxxxxxxx
Fixes: bd726c90b6b8 ("Allow stack to grow up to address space limit")
Signed-off-by: Helge Deller <deller@xxxxxx>
Reported-by: JÃrn Engel <joern@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
mm/mmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 3c4e4d7..d042e25 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2132,7 +2132,7 @@ 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)
+ if (address >= (TASK_SIZE & PAGE_MASK))
return -ENOMEM;
address += PAGE_SIZE;

--
2.8.0.rc2.1.gbe9624a