linux-kernel - [PATCH] fs: sysfs: don't pass count == 0 to bin file readers

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Message-Id: <1432243276-27733-1-git-send-email-vz@mleia.com>
Date:	Fri, 22 May 2015 00:21:16 +0300
From:	Vladimir Zapolskiy <vz@...ia.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] fs: sysfs: don't pass count == 0 to bin file readers

If count == 0 bytes are requested by a reader, sysfs_kf_bin_read()
deliberately returns 0 without passing a potentially harmful value to
some externally defined underlying battr->read() function.

However in case of (pos == size && count) the next clause always sets
count to 0 and this value is handed over to battr->read().

The change intends to make obsolete (and remove later) a redundant
sanity check in battr->read(), if it is present, or add more
protection to struct bin_attribute users, who does not care about
input arguments.

Signed-off-by: Vladimir Zapolskiy <vz@...ia.com>
---
 fs/sysfs/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 7c2867b..6c95628 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -90,7 +90,7 @@ static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
 		return 0;

 	if (size) {
-		if (pos > size)
+		if (pos >= size)
 			return 0;
 		if (pos + count > size)
 			count = size - pos;
-- 
1.7.10.4

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