linux-kernel - [PATCH v3 13/33] test_printf: Drop requirement that sprintf not write past nul

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat,  4 Jun 2022 15:30:22 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Kent Overstreet <kent.overstreet@...il.com>, pmladek@...e.com,
        rostedt@...dmis.org
Subject: [PATCH v3 13/33] test_printf: Drop requirement that sprintf not write past nul

The current test code checks that sprintf never writes past the
terminating nul. This is a rather strange requirement, completely
separate from writing past the end of the buffer, which of course we
can't do: writing anywhere to the buffer passed to snprintf, within size
of course, should be perfectly fine.

Since this check has no documentation as to where it comes from or what
depends on it, and it's getting in the way of further refactoring
(printf_spec handling is right now scattered massively throughout the
code, and we'd like to consolidate it) - delete it.

Also, many current pretty-printers building up their output on the
stack, and then copy it to the actual output buffer - by eliminating
this requirement we can kill those extra buffers.

Signed-off-by: Kent Overstreet <kent.overstreet@...il.com>
---
 lib/test_printf.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/lib/test_printf.c b/lib/test_printf.c
index ff833870f5..a702dd5dc0 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -78,12 +78,6 @@ do_test(int bufsize, const char *expect, int elen,
 		return 1;
 	}

-	if (memchr_inv(test_buffer + written + 1, FILL_CHAR, BUF_SIZE + PAD_SIZE - (written + 1))) {
-		pr_warn("vsnprintf(buf, %d, \"%s\", ...) wrote beyond the nul-terminator\n",
-			bufsize, fmt);
-		return 1;
-	}
-
 	if (memcmp(test_buffer, expect, written)) {
 		pr_warn("vsnprintf(buf, %d, \"%s\", ...) wrote '%s', expected '%.*s'\n",
 			bufsize, fmt, test_buffer, written, expect);
-- 
2.36.0