Commit 08161786 authored by Vitaly Mayatskikh's avatar Vitaly Mayatskikh Committed by Linus Torvalds

pagemap: require aligned-length, non-null reads of /proc/pid/pagemap

The intention of commit aae8679b
("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: default avatarVitaly Mayatskikh <v.mayatskih@gmail.com>
Cc: Thomas Tuttle <ttuttle@google.com>
Acked-by: default avatarMatt Mackall <mpm@selenic.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b827e496
...@@ -665,6 +665,10 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, ...@@ -665,6 +665,10 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
goto out_task; goto out_task;
ret = 0; ret = 0;
if (!count)
goto out_task;
mm = get_task_mm(task); mm = get_task_mm(task);
if (!mm) if (!mm)
goto out_task; goto out_task;
......
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