From: Andrey Vagin Date: Wed, 9 Mar 2011 23:22:23 +0000 (-0800) Subject: x86/mm: Handle mm_fault_error() in kernel space X-Git-Tag: v2.6.35.12~86 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7838ead2b8f913f82d2b1d7f51e12d9ff1d6d936;p=thirdparty%2Fkernel%2Fstable.git x86/mm: Handle mm_fault_error() in kernel space 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 Signed-off-by: Andrew Morton Signed-off-by: Andi Kleen Cc: "H. Peter Anvin" Cc: Linus Torvalds LKML-Reference: <201103092322.p29NMNPH001682@imap1.linux-foundation.org> Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 4c4508e8a2043..544ed251a40c4 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))