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Subject[patch 27/58] pagemap: require aligned-length, non-null reads of /proc/pid/pagemap
2.6.29-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Vitaly Mayatskikh <v.mayatskih@gmail.com>

commit 0816178638c15ce5472d39d771a96860dff4141a upstream.

The intention of commit aae8679b0ebcaa92f99c1c3cb0cd651594a43915
("pagemap: fix bug in add_to_pagemap, require aligned-length reads of
/proc/pid/pagemap") was to force reads of /proc/pid/pagemap to be a
multiple of 8 bytes, but now it allows to read 0 bytes, which actually
puts some data to user's buffer. According to POSIX, if count is zero,
read() should return zero and has no other results.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Cc: Thomas Tuttle <ttuttle@google.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/proc/task_mmu.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -663,6 +663,10 @@ static ssize_t pagemap_read(struct file
goto out_task;

ret = 0;
+
+ if (!count)
+ goto out_task;
+
mm = get_task_mm(task);
if (!mm)
goto out_task;



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