Bug 224143 - [PATCH] fmtcheck(3) misjudges format string with fewer arguments
Summary: [PATCH] fmtcheck(3) misjudges format string with fewer arguments
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: bin (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Some People
Assignee: freebsd-bugs mailing list
URL:
Keywords: patch
Depends on:
Blocks:
 
Reported: 2017-12-06 12:57 UTC by Rin Okuyama
Modified: 2017-12-14 10:55 UTC (History)
1 user (show)

See Also:


Attachments
Correct oversight of wrong format string with fewer arguments. (267 bytes, patch)
2017-12-06 12:57 UTC, Rin Okuyama
no flags Details | Diff

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Description Rin Okuyama 2017-12-06 12:57:26 UTC
Created attachment 188583 [details]
Correct oversight of wrong format string with fewer arguments.

fmtcheck(3) misjudges some format strings as valid when they have fewer arguments
than default format strings have:

----
% uname -a
FreeBSD freebsd 12.0-CURRENT FreeBSD 12.0-CURRENT #0 r325595: Thu Nov  9 16:03:47 UTC 2017     root@releng3.nyi.freebsd.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC  amd64
% cat test.c
#include <stdio.h>
int main() {
        const char *s1 = "One argument: %d", *s2 = "Two arguments: %d %d";
        printf("%s\n", fmtcheck(s1, s2));
        printf("%s\n", fmtcheck(s2, s1));
}
% cc test.c && ./a.out
One argument: %d
One argument: %d
----

Here, the first line should be "Two arguments: %d %d".

Please apply the attached patch, which has been committed to NetBSD by myself:
http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/fmtcheck.c#rev1.11
Comment 1 Rin Okuyama 2017-12-14 10:55:41 UTC
Sorry the patch posted here has been reverted in NetBSD. It turned out that
some applications depends on the current behavior; they assume that fmtcheck(3)
does not complain unused trailing arguments.

The description in manpage is misleading. I will send a patch as soon as it
gets committed to NetBSD.