Re: [PATCH] libfile: null-terminate buffer as expected

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Sep 16, 2019 at 08:48:13PM +0200, Ahmad Fatoum wrote:
> On 9/16/19 8:38 PM, Ahmad Fatoum wrote:
> > strim calls strlen on buf internally which is undefined because buf
> > is not null-terminated. Fix this.
> 
> Please dismiss... read_file_2 has its buffer allocated with calloc,
> thus nothing to see here...

except this:

---------------------------8<-------------------------------

From b3692899dd20e85368aea114f0984cf204f24356 Mon Sep 17 00:00:00 2001
From: Sascha Hauer <s.hauer@pengutronix.de>
Date: Tue, 17 Sep 2019 09:46:46 +0200
Subject: [PATCH] libfile: Document that read_file() returns a terminated
 buffer

read_file() and read_file_2() return a '\0' terminated buffer to make
sure the buffer is usable as a string. Other code like read_file_line()
depends on this behaviour, so document it explicitly.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 lib/libfile.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/libfile.c b/lib/libfile.c
index 172602377f..648d409a01 100644
--- a/lib/libfile.c
+++ b/lib/libfile.c
@@ -158,7 +158,9 @@ EXPORT_SYMBOL_GPL(read_file_line);
  * bytes are read. The actual read size is returned in @size. -EFBIG is
  * returned if the file is bigger than @max_size, but the buffer is read
  * anyway up to @max_size in this case. Free the buffer with free() after
- * usage.
+ * usage. The allocated buffer is actually one byte bigger than the file
+ * and the extra byte is initialized to '\0' so that the returned buffer
+ * can safely be interpreted as a string.
  *
  * Return: 0 for success, or negative error code. -EFBIG is returned
  * when the file has been bigger than max_size.
-- 
2.23.0

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