| From | Andi Kleen <> | Subject | [PATCH] [188/275] x86/mm: Handle mm_fault_error() in kernel space | Date | Wed, 30 Mar 2011 14:07:11 -0700 (PDT) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Andrey Vagin <avagin@openvz.org>
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> Signed-off-by: Andi Kleen <ak@linux.intel.com> 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: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/mm/fault.c | 7 +++++++ 1 file changed, 7 insertions(+)
Index: linux-2.6.35.y/arch/x86/mm/fault.c =================================================================== --- linux-2.6.35.y.orig/arch/x86/mm/fault.c 2011-03-29 22:50:46.520068086 -0700 +++ linux-2.6.35.y/arch/x86/mm/fault.c 2011-03-29 23:03:02.185244254 -0700 @@ -831,6 +831,13 @@ 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))
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