| Message ID | 1368702394-1737-1-git-send-email-steve.capper@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, May 16, 2013 at 12:06:34PM +0100, Steve Capper wrote: > If one reads /proc/$PID/smaps, the mmap_sem belonging to the > address space of the task being examined is locked for reading. > All the pages of the vmas belonging to the task's address space > are then walked with this lock held. > > If a gate_vma is present in the architecture, it too is examined > by the fs/proc/task_mmu.c code. As gate_vma doesn't belong to the > address space of the task though, its pages are not walked. > > A recent cleanup (commit f6604efe) of the gate_vma initialisation > code set the vm_mm value to &init_mm. Unfortunately a non-NULL > vm_mm value in the gate_vma will cause the task_mmu code to attempt > to walk the pages of the gate_vma (with no mmap-sem lock held). If > one enables Transparent Huge Page support and vm debugging, this > will then cause OOPses as pmd_trans_huge_lock is called without > mmap_sem being locked. > > This patch removes the .vm_mm value from gate_vma, restoring the > original behaviour of the task_mmu code. This looks fine - x86 also sets .vm_mm to NULL here. So please put it in my patch system. Does this need to be applied to stable kernels as well? If so, please mark it with Cc: <stable@vger.kernel.org> (but do not send it to that address). Also, it'd be worth checking which stable kernels it needs to be applied to. Thanks.
On Thu, May 16, 2013 at 03:36:38PM +0100, Russell King - ARM Linux wrote: > On Thu, May 16, 2013 at 12:06:34PM +0100, Steve Capper wrote: [ ... ] > > This looks fine - x86 also sets .vm_mm to NULL here. So please put > it in my patch system. Does this need to be applied to stable > kernels as well? If so, please mark it with Cc: <stable@vger.kernel.org> > (but do not send it to that address). Also, it'd be worth checking > which stable kernels it needs to be applied to. > > Thanks. Thank you Russell, I couldn't see any branches in linux-stable that need this patch. The patch is now in your system with id 7727/1. Cheers,
On Thu, May 16, 2013 at 12:06:34PM +0100, Steve Capper wrote: > If one reads /proc/$PID/smaps, the mmap_sem belonging to the > address space of the task being examined is locked for reading. > All the pages of the vmas belonging to the task's address space > are then walked with this lock held. > > If a gate_vma is present in the architecture, it too is examined > by the fs/proc/task_mmu.c code. As gate_vma doesn't belong to the > address space of the task though, its pages are not walked. > > A recent cleanup (commit f6604efe) of the gate_vma initialisation > code set the vm_mm value to &init_mm. Unfortunately a non-NULL > vm_mm value in the gate_vma will cause the task_mmu code to attempt > to walk the pages of the gate_vma (with no mmap-sem lock held). If > one enables Transparent Huge Page support and vm debugging, this > will then cause OOPses as pmd_trans_huge_lock is called without > mmap_sem being locked. > > This patch removes the .vm_mm value from gate_vma, restoring the > original behaviour of the task_mmu code. > > Signed-off-by: Steve Capper <steve.capper@linaro.org> > --- > arch/arm/kernel/process.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c > index f219703..282de48 100644 > --- a/arch/arm/kernel/process.c > +++ b/arch/arm/kernel/process.c > @@ -411,7 +411,6 @@ static struct vm_area_struct gate_vma = { > .vm_start = 0xffff0000, > .vm_end = 0xffff0000 + PAGE_SIZE, > .vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYEXEC, > - .vm_mm = &init_mm, > }; > > static int __init gate_vma_init(void) Thanks to the wonders of Mimecrap, which decided to sit on most of my email yesterday, I only just received this patch. I see it's in the patch system, but for the record: Acked-by: Will Deacon <will.deacon@arm.com> Cheers, Will
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index f219703..282de48 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -411,7 +411,6 @@ static struct vm_area_struct gate_vma = { .vm_start = 0xffff0000, .vm_end = 0xffff0000 + PAGE_SIZE, .vm_flags = VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYEXEC, - .vm_mm = &init_mm, }; static int __init gate_vma_init(void)
If one reads /proc/$PID/smaps, the mmap_sem belonging to the address space of the task being examined is locked for reading. All the pages of the vmas belonging to the task's address space are then walked with this lock held. If a gate_vma is present in the architecture, it too is examined by the fs/proc/task_mmu.c code. As gate_vma doesn't belong to the address space of the task though, its pages are not walked. A recent cleanup (commit f6604efe) of the gate_vma initialisation code set the vm_mm value to &init_mm. Unfortunately a non-NULL vm_mm value in the gate_vma will cause the task_mmu code to attempt to walk the pages of the gate_vma (with no mmap-sem lock held). If one enables Transparent Huge Page support and vm debugging, this will then cause OOPses as pmd_trans_huge_lock is called without mmap_sem being locked. This patch removes the .vm_mm value from gate_vma, restoring the original behaviour of the task_mmu code. Signed-off-by: Steve Capper <steve.capper@linaro.org> --- arch/arm/kernel/process.c | 1 - 1 file changed, 1 deletion(-)