On Thu 25-07-13 18:25:34, Johannes Weiner wrote:
> Kernel faults are expected to handle OOM conditions gracefully (gup,
> uaccess etc.), so they should never invoke the OOM killer. Reserve
> this for faults triggered in user context when it is the only option.
>
> Most architectures already do this, fix up the remaining few.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
I didn't go over all architectures to check whether something slipped
through but the converted ones look OK to me.
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> arch/arm/mm/fault.c | 14 +++++++-------
> arch/arm64/mm/fault.c | 14 +++++++-------
> arch/avr32/mm/fault.c | 2 +-
> arch/mips/mm/fault.c | 2 ++
> arch/um/kernel/trap.c | 2 ++
> arch/unicore32/mm/fault.c | 14 +++++++-------
> 6 files changed, 26 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index c97f794..217bcbf 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -349,6 +349,13 @@ retry:
> if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
> return 0;
>
> + /*
> + * If we are in kernel mode at this point, we
> + * have no context to handle this fault with.
> + */
> + if (!user_mode(regs))
> + goto no_context;
> +
> if (fault & VM_FAULT_OOM) {
> /*
> * We ran out of memory, call the OOM killer, and return to
> @@ -359,13 +366,6 @@ retry:
> return 0;
> }
>
> - /*
> - * If we are in kernel mode at this point, we
> - * have no context to handle this fault with.
> - */
> - if (!user_mode(regs))
> - goto no_context;
> -
> if (fault & VM_FAULT_SIGBUS) {
> /*
> * We had some memory, but were unable to
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 0ecac89..dab1cfd 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -294,6 +294,13 @@ retry:
> VM_FAULT_BADACCESS))))
> return 0;
>
> + /*
> + * If we are in kernel mode at this point, we have no context to
> + * handle this fault with.
> + */
> + if (!user_mode(regs))
> + goto no_context;
> +
> if (fault & VM_FAULT_OOM) {
> /*
> * We ran out of memory, call the OOM killer, and return to
> @@ -304,13 +311,6 @@ retry:
> return 0;
> }
>
> - /*
> - * If we are in kernel mode at this point, we have no context to
> - * handle this fault with.
> - */
> - if (!user_mode(regs))
> - goto no_context;
> -
> if (fault & VM_FAULT_SIGBUS) {
> /*
> * We had some memory, but were unable to successfully fix up
> diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
> index b2f2d2d..2ca27b0 100644
> --- a/arch/avr32/mm/fault.c
> +++ b/arch/avr32/mm/fault.c
> @@ -228,9 +228,9 @@ no_context:
> */
> out_of_memory:
> up_read(&mm->mmap_sem);
> - pagefault_out_of_memory();
> if (!user_mode(regs))
> goto no_context;
> + pagefault_out_of_memory();
> return;
>
> do_sigbus:
> diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
> index 85df1cd..94d3a31 100644
> --- a/arch/mips/mm/fault.c
> +++ b/arch/mips/mm/fault.c
> @@ -241,6 +241,8 @@ out_of_memory:
> * (which will retry the fault, or kill us if we got oom-killed).
> */
> up_read(&mm->mmap_sem);
> + if (!user_mode(regs))
> + goto no_context;
> pagefault_out_of_memory();
> return;
>
> diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
> index 089f398..b2f5adf 100644
> --- a/arch/um/kernel/trap.c
> +++ b/arch/um/kernel/trap.c
> @@ -124,6 +124,8 @@ out_of_memory:
> * (which will retry the fault, or kill us if we got oom-killed).
> */
> up_read(&mm->mmap_sem);
> + if (!is_user)
> + goto out_nosemaphore;
> pagefault_out_of_memory();
> return 0;
> }
> diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
> index f9b5c10..8ed3c45 100644
> --- a/arch/unicore32/mm/fault.c
> +++ b/arch/unicore32/mm/fault.c
> @@ -278,6 +278,13 @@ retry:
> (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
> return 0;
>
> + /*
> + * If we are in kernel mode at this point, we
> + * have no context to handle this fault with.
> + */
> + if (!user_mode(regs))
> + goto no_context;
> +
> if (fault & VM_FAULT_OOM) {
> /*
> * We ran out of memory, call the OOM killer, and return to
> @@ -288,13 +295,6 @@ retry:
> return 0;
> }
>
> - /*
> - * If we are in kernel mode at this point, we
> - * have no context to handle this fault with.
> - */
> - if (!user_mode(regs))
> - goto no_context;
> -
> if (fault & VM_FAULT_SIGBUS) {
> /*
> * We had some memory, but were unable to
> --
> 1.8.3.2
>
--
Michal Hocko
SUSE Labs
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