Messages in this thread Patch in this message | | | From | Andrey Vagin <> | Subject | [PATCH] mm: handle mm_fault_error in kernel space (v2) | Date | Tue, 8 Mar 2011 18:59:25 +0300 |
| |
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 <avagin@openvz.org> --- 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
| |