| From | Paul Gortmaker <> | Subject | [34-longterm 170/247] x86/mm: Handle mm_fault_error() in kernel space | Date | Thu, 23 Jun 2011 13:33:58 -0400 |
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From: Andrey Vagin <avagin@openvz.org>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. If you see a problem with using this for longterm, please comment. -------------------
commit f86268549f424f83b9eb0963989270e14fbfc3de upstream.
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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> LKML-Reference: <201103092322.p29NMNPH001682@imap1.linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- 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 4c4508e..544ed25 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -831,6 +831,13 @@ 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)) -- 1.7.4.4
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