The patch titled
proc: put check_mem_permission after __get_free_page in mem_write
has been added to the -mm tree. Its filename is
proc-put-check_mem_permission-after-__get_free_page-in-mem_write.patch
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------------------------------------------------------
Subject: proc: put check_mem_permission after __get_free_page in mem_write
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
It whould be better if put check_mem_permission after __get_free_page in
mem_write, to be same as function mem_read.
Hugh Dickins explained the reason.
check_mem_permission gets a reference to the mm. If we __get_free_page
after check_mem_permission, imagine what happens if the system is out
of memory, and the mm we're looking at is selected for killing by the
OOM killer: while we wait in __get_free_page for more memory, no memory
is freed from the selected mm because it cannot reach exit_mmap while
we hold that reference.
Reported-by: Jovi Zhang <bookjovi@xxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: Stephen Wilson <wilsons@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff -puN fs/proc/base.c~proc-put-check_mem_permission-after-__get_free_page-in-mem_write fs/proc/base.c
--- a/fs/proc/base.c~proc-put-check_mem_permission-after-__get_free_page-in-mem_write
+++ a/fs/proc/base.c
@@ -894,20 +894,20 @@ static ssize_t mem_write(struct file * f
if (!task)
goto out_no_task;
+ copied = -ENOMEM;
+ page = (char *)__get_free_page(GFP_TEMPORARY);
+ if (!page)
+ goto out_task;
+
mm = check_mem_permission(task);
copied = PTR_ERR(mm);
if (IS_ERR(mm))
- goto out_task;
+ goto out_free;
copied = -EIO;
if (file->private_data != (void *)((long)current->self_exec_id))
goto out_mm;
- copied = -ENOMEM;
- page = (char *)__get_free_page(GFP_TEMPORARY);
- if (!page)
- goto out_mm;
-
copied = 0;
while (count > 0) {
int this_len, retval;
@@ -929,9 +929,11 @@ static ssize_t mem_write(struct file * f
count -= retval;
}
*ppos = dst;
- free_page((unsigned long) page);
+
out_mm:
mmput(mm);
+out_free:
+ free_page((unsigned long) page);
out_task:
put_task_struct(task);
out_no_task:
_
Patches currently in -mm which might be from kosaki.motohiro@xxxxxxxxxxxxxx are
origin.patch
oom-use-pte-pages-in-oom-score.patch
mm-per-node-vmstat-show-proper-vmstats.patch
mm-per-node-vmstat-show-proper-vmstats-fix.patch
mm-increase-reclaim_distance-to-30.patch
mm-introduce-wait_on_page_locked_killable.patch
x86mm-make-pagefault-killable.patch
mm-mem-hotplug-fix-section-mismatch-setup_per_zone_inactive_ratio-should-be-__meminit.patch
mm-mem-hotplug-recalculate-lowmem_reserve-when-memory-hotplug-occur.patch
mm-mem-hotplug-update-pcp-stat_threshold-when-memory-hotplug-occur.patch
mm-mem-hotplug-update-pcp-stat_threshold-when-memory-hotplug-occur-fix.patch
mm-convert-vma-vm_flags-to-64-bit.patch
mm-add-__nocast-attribute-to-vm_flags.patch
fremap-convert-vm_flags-to-unsigned-long-long.patch
procfs-convert-vm_flags-to-unsigned-long-long.patch
oom-replace-pf_oom_origin-with-toggling-oom_score_adj.patch
oom-replace-pf_oom_origin-with-toggling-oom_score_adj-update.patch
mm-mmu_gather-rework.patch
powerpc-mmu_gather-rework.patch
sparc-mmu_gather-rework.patch
s390-mmu_gather-rework.patch
arm-mmu_gather-rework.patch
sh-mmu_gather-rework.patch
ia64-mmu_gather-rework.patch
um-mmu_gather-rework.patch
mm-now-that-all-old-mmu_gather-code-is-gone-remove-the-storage.patch
mm-powerpc-move-the-rcu-page-table-freeing-into-generic-code.patch
mm-extended-batches-for-generic-mmu_gather.patch
lockdep-mutex-provide-mutex_lock_nest_lock.patch
mm-remove-i_mmap_lock-lockbreak.patch
mm-convert-i_mmap_lock-to-a-mutex.patch
mm-revert-page_lock_anon_vma-lock-annotation.patch
mm-improve-page_lock_anon_vma-comment.patch
mm-use-refcounts-for-page_lock_anon_vma.patch
mm-convert-anon_vma-lock-to-a-mutex.patch
mm-optimize-page_lock_anon_vma-fast-path.patch
mn10300-replace-mm-cpu_vm_mask-with-mm_cpumask.patch
tile-replace-mm-cpu_vm_mask-with-mm_cpumask.patch
mm-convert-mm-cpu_vm_cpumask-into-cpumask_var_t.patch
mm-convert-mm-cpu_vm_cpumask-into-cpumask_var_t-checkpatch-fixes.patch
mem-hotplug-call-isolate_lru_page-with-elevated-refcount.patch
mem-hwpoison-fix-page-refcount-around-isolate_lru_page.patch
mm-strictly-require-elevated-page-refcount-in-isolate_lru_page.patch
mm-check-if-any-page-in-a-pageblock-is-reserved-before-marking-it-migrate_reserve.patch
mm-check-if-any-page-in-a-pageblock-is-reserved-before-marking-it-migrate_reserve-fix.patch
readahead-readahead-page-allocations-are-ok-to-fail.patch
vmscan-change-shrink_slab-interfaces-by-passing-shrink_control.patch
vmscan-change-shrinker-api-by-passing-shrink_control-struct.patch
mm-batch-activate_page-to-reduce-lock-contention.patch
alpha-replace-with-new-cpumask-apis.patch
m32r-convert-cpumask-api.patch
m32r-fix-spin_lock_irqsave-misuse.patch
m32r-remove-redundant-declaration.patch
sparse-define-dummy-build_bug_on-definition-for-sparse.patch
sparse-define-__must_be_array-for-__checker__.patch
sparse-undef-__compiletime_warningerror-if-__checker__-is-defined.patch
mm-move-enum-vm_event_item-into-a-standalone-header-file.patch
memcg-count-the-soft_limit-reclaim-in-global-background-reclaim.patch
memcg-add-stats-to-monitor-soft_limit-reclaim.patch
add-the-pagefault-count-into-memcg-stats.patch
add-the-pagefault-count-into-memcg-stats-fix.patch
vmscanmemcg-memcg-aware-swap-token.patch
vmscanmemcg-memcg-aware-swap-token-fix.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-cpusets-initialize-spread-rotor-lazily.patch
proc-put-check_mem_permission-after-__get_free_page-in-mem_write.patch
cpumask-convert-for_each_cpumask-with-for_each_cpu.patch
cpumask-convert-cpumask_of_cpu-to-cpumask_of.patch
kexec-remove-kmsg_dump_kexec.patch
kexec-remove-kmsg_dump_kexec-fix.patch
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