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authorDerek <denc716@gmail.com>2015-04-15 16:13:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-15 16:35:18 -0700
commit12215182c80c06ab3c69969abba6e4a834493cd8 (patch)
tree3f9d2d28d761d676750bbdf22bae59cb73b0d568 /mm
parent7d61bfe8fddecad76eb37cc477aab369c5c81ed3 (diff)
mremap should return -ENOMEM when __vm_enough_memory fail
Recently I straced bash behavior in this dd zero pipe to read test, in part of testing under vm.overcommit_memory=2 (OVERCOMMIT_NEVER mode): # dd if=/dev/zero | read x The bash sub shell is calling mremap to reallocate more and more memory untill it finally failed -ENOMEM (I expect), or to be killed by system OOM killer (which should not happen under OVERCOMMIT_NEVER mode); But the mremap system call actually failed of -EFAULT, which is a surprise to me, I think it's supposed to be -ENOMEM? then I wrote this piece of C code testing confirmed it: https://gist.github.com/crquan/326bde37e1ddda8effe5 $ ./remap allocated one page @0x7f686bf71000, (PAGE_SIZE: 4096) grabbed 7680512000 bytes of memory (1875125 pages) @ 00007f6690993000. mremap failed Bad address (14). The -EFAULT comes from the branch of security_vm_enough_memory_mm failure, underlyingly it calls __vm_enough_memory which returns only 0 for success or -ENOMEM; So why vma_to_resize needs to return -EFAULT in this case? this sounds like a mistake to me. Some more digging into git history: 1) Before commit 119f657c7 ("RLIMIT_AS checking fix") in May 1 2005 (pre 2.6.12 days) it was returning -ENOMEM for this failure; 2) but commit 119f657c7 ("untangling do_mremap(), part 1") changed it accidentally, to what ever is preserved in local ret, which happened to be -EFAULT, in a previous assignment; 3) then in commit 54f5de709 code refactoring, it's explicitly returning -EFAULT, should be wrong. Signed-off-by: Derek Che <crquan@ymail.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mremap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 2dc44b1cb1df..1fb0f9069653 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -381,7 +381,7 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
if (vma->vm_flags & VM_ACCOUNT) {
unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
if (security_vm_enough_memory_mm(mm, charged))
- goto Efault;
+ goto Enomem;
*p = charged;
}

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