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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2011-05-26 16:25:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-26 17:12:37 -0700
commit98bc93e505c03403479c6669c4ff97301cee6199 (patch)
tree0b6bf39cd6107d536b55fd245b9905cb5baa4e74
parent30cd8903913dac7b0918807cac46be3ecde5a5a7 (diff)
downloadvexpress-lsk-98bc93e505c03403479c6669c4ff97301cee6199.tar.gz
proc: fix pagemap_read() error case
Currently, pagemap_read() has three error and/or corner case handling mistake. (1) If ppos parameter is wrong, mm refcount will be leak. (2) If count parameter is 0, mm refcount will be leak too. (3) If the current task is sleeping in kmalloc() and the system is out of memory and oom-killer kill the proc associated task, mm_refcount prevent the task free its memory. then system may hang up. <Quote Hugh's explain why we shold call kmalloc() before get_mm()> 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. This patch fixes the above three. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jovi Zhang <bookjovi@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Stephen Wilson <wilsons@start.ca> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/task_mmu.c19
1 files changed, 9 insertions, 10 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 30a6a72d05b..25b6a887adb 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -771,18 +771,12 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!task)
goto out;
- mm = mm_for_maps(task);
- ret = PTR_ERR(mm);
- if (!mm || IS_ERR(mm))
- goto out_task;
-
ret = -EINVAL;
/* file position must be aligned */
if ((*ppos % PM_ENTRY_BYTES) || (count % PM_ENTRY_BYTES))
goto out_task;
ret = 0;
-
if (!count)
goto out_task;
@@ -790,7 +784,12 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
ret = -ENOMEM;
if (!pm.buffer)
- goto out_mm;
+ goto out_task;
+
+ mm = mm_for_maps(task);
+ ret = PTR_ERR(mm);
+ if (!mm || IS_ERR(mm))
+ goto out_free;
pagemap_walk.pmd_entry = pagemap_pte_range;
pagemap_walk.pte_hole = pagemap_pte_hole;
@@ -833,7 +832,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
len = min(count, PM_ENTRY_BYTES * pm.pos);
if (copy_to_user(buf, pm.buffer, len)) {
ret = -EFAULT;
- goto out_free;
+ goto out_mm;
}
copied += len;
buf += len;
@@ -843,10 +842,10 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!ret || ret == PM_END_OF_BUFFER)
ret = copied;
-out_free:
- kfree(pm.buffer);
out_mm:
mmput(mm);
+out_free:
+ kfree(pm.buffer);
out_task:
put_task_struct(task);
out: