mm_fault_error() should not execute oom-killer, if page fault occurs
in kernel space. E.g. in copy_from_user/copy_to_user.
This would happen if we find ourselves in OOM on a copy_to_user(),
or a copy_from_user() which faults.
Without this patch, the kernels hangs up in copy_from_user, because
OOM killer sends SIG_KILL to current process, but it can't handle a
signal while in syscall, then the kernel returns to copy_from_user,
reexcute current command and provokes page_fault again.
With this patch the kernel return -EFAULT from copy_from_user.
The code, which checks that page fault occurred in kernel space, has been
copied from do_sigbus.
This situation is handled by the same way on powerpc, xtensa, tile, ...
Signed-off-by: Andrey Vagin <[email protected]>
---
arch/x86/mm/fault.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 7d90ceb..ffc7be1 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -828,6 +828,13 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
unsigned long address, unsigned int fault)
{
if (fault & VM_FAULT_OOM) {
+ /* Kernel mode? Handle exceptions or die: */
+ if (!(error_code & PF_USER)) {
+ up_read(¤t->mm->mmap_sem);
+ no_context(regs, error_code, address);
+ return;
+ }
+
out_of_memory(regs, error_code, address);
} else {
if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
--
1.7.1