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[PATCH 13/18] exec: make exec path waiting for mmap_sem killable

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From: Michal Hocko <mhocko@suse.com>

setup_arg_pages requires mmap_sem for write. If the waiting task
gets killed by the oom killer it would block oom_reaper from
asynchronous address space reclaim and reduce the chances of timely
OOM resolving. Wait for the lock in the killable mode and return with
EINTR if the task got killed while waiting. All the callers are already
handling error path and the fatal signal doesn't need any additional
treatment.

The same applies to __bprm_mm_init.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 fs/exec.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 2f44590d88a9..d7a6ff09bb7a 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -267,7 +267,10 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
 	if (!vma)
 		return -ENOMEM;
 
-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem)) {
+		err = -EINTR;
+		goto err_free;
+	}
 	vma->vm_mm = mm;
 
 	/*
@@ -294,6 +297,7 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
 	return 0;
 err:
 	up_write(&mm->mmap_sem);
+err_free:
 	bprm->vma = NULL;
 	kmem_cache_free(vm_area_cachep, vma);
 	return err;
@@ -700,7 +704,9 @@ int setup_arg_pages(struct linux_binprm *bprm,
 		bprm->loader -= stack_shift;
 	bprm->exec -= stack_shift;
 
-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
+
 	vm_flags = VM_STACK_FLAGS;
 
 	/*
-- 
2.8.0.rc3

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[PATCH 0/18] change mmap_sem taken for write killable v2 Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 09/18] ipc, shm: make shmem attach/detach wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 07/18] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 13/18] exec: make exec path waiting for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 06/18] mm: make vm_brk killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 18/18] drm/amdgpu: make amdgpu_mn_get wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 03/18] mm: make vm_munmap killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 08/18] mm, fork: make dup_mmap wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
    Re: [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem  killable Alex Thorlton <athorlton@sgi.com> - 2016-04-26 17:20 +0200
  [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 10/18] vdso: make arch_setup_additional_pages wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 02/18] mm: make vm_mmap killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 11/18] coredump: make coredump_wait wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 12/18] aio: make aio_setup_ring killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 04/18] mm, aout: handle vm_brk failures Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200
  [PATCH 05/18] mm, elf: handle vm_brk error Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200
  [PATCH 01/18] mm: Make mmap_sem for write waits killable for mm syscalls Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200

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