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Re: bin/38201: Potential lack of null termination when copying a string
The following reply was made to PR bin/38201; it has been noted by GNATS.
From: David Laight <david%l8s.co.uk@localhost>
Subject: Re: bin/38201: Potential lack of null termination when copying a string
Date: Tue, 11 Mar 2008 18:41:51 +0000
On Sat, Mar 08, 2008 at 10:25:46PM +0000, David Holland wrote:
> On Sat, Mar 08, 2008 at 07:55:01PM +0000, netbsd%happyjack.org@localhost
> > [who/utmpentry.c]
> > In two places, the wrong object is null-terminated after a
> > strncpy(), resulting in a potential lack of null termination.
> Good catch... but it turns out that those null terminations are
> neither necessary nor useful. I will clean up the mess...
Actually they were also wrong!
(void)strncpy(e->host, up->ut_host, sizeof(up->ut_host));
- e->name[sizeof(e->name) - 1] = '\0';
+ e->host[sizeof(e->host) - 1] = '\0';
Since e->host is guaranteed to be longer than up->ut_host, and strncpy
is used because up->ut_host might not be null terminated, the correct
line would be:
e->host[sizeof up->ut_host - 1] = 0;
Of course, the code worked because the buffer had just been calloc'ed.
David Laight: david%l8s.co.uk@localhost
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