linux-kernel - [PATCH] pagemap: require aligned-length, non-null reads of /proc/pid/pagemap

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Message-ID: <87eivn5q3r.wl%vmayatsk@redhat.com>
Date:	Mon, 20 Apr 2009 16:58:32 +0200
From:	Vitaly Mayatskikh <v.mayatskih@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Thomas Tuttle <ttuttle@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] pagemap: require aligned-length, non-null reads of /proc/pid/pagemap

The intention of commit aae8679b0ebcaa92f99c1c3cb0cd651594a43915 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@...il.com>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 39e4ad4..6f61b7c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -665,6 +665,10 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 		goto out_task;
 
 	ret = 0;
+
+	if (!count)
+		goto out_task;
+
 	mm = get_task_mm(task);
 	if (!mm)
 		goto out_task;

-- 
wbr, Vitaly
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