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From 59b280ebe22eceaf4250cb3b776674619a4d4ece Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
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Date: Mon, 5 Feb 2018 11:07:41 +0100
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Subject: [PATCH] warnquota: Fix comparing user name to non-null-terminated
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utmp.ut_user
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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GCC 8 with GNU libc 2.27 warns:
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gcc -DHAVE_CONFIG_H -I. -I/usr/include/dbus-1.0 -I/usr/lib64/dbus-1.0/include -I/usr/include/libnl3 -g -O2 -Wall -fPIC -I/usr/include/tirpc -c -o quota_nld-quota_nld.o `test -f 'quota_nld.c' || echo './'`quota_nld.c
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quota_nld.c: In function ‘write_console_warning’:
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quota_nld.c:273:7: warning: ‘strcmp’ argument 2 declared attribute ‘nonstring’ [-Wstringop-overflow=]
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if (strcmp(user, uent->ut_user))
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^~~~~~~~~~~~~~~~~~~~~~~~~~~
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In file included from /usr/include/utmp.h:29,
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from quota_nld.c:23:
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/usr/include/bits/utmp.h:65:8: note: argument ‘ut_user’ declared here
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char ut_user[UT_NAMESIZE]
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^~~~~~~
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This is because ut_user value misses the terminating null byte if it
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fits exactly into ut_user array, as document in utmp(5):
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String fields are terminated by a null byte ('\0') if they are
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shorter than the size of the field.
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Recent GCC and glibc recevied compile-time checks and annotations
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(__attribute_nonstring_) that catches these mistakes.
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This patch fixes it by using strncmp(3) and by ignoring user names
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that does not fit into utmp log format. It's better not to warn than
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spamming unrelated user.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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Signed-off-by: Jan Kara <jack@suse.cz>
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---
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quota_nld.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/quota_nld.c b/quota_nld.c
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index ea541e0..8559f25 100644
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--- a/quota_nld.c
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+++ b/quota_nld.c
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@@ -262,6 +262,8 @@ static void write_console_warning(struct quota_warning *warn)
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warn->warntype == QUOTA_NL_BSOFTBELOW) && !(flags & FL_PRINTBELOW))
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return;
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uid2user(warn->caused_id, user);
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+ if (strlen(user) > UT_NAMESIZE)
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+ goto skip_utmp;
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strcpy(dev, "/dev/");
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setutent();
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@@ -270,7 +272,7 @@ static void write_console_warning(struct quota_warning *warn)
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if (uent->ut_type != USER_PROCESS)
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continue;
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/* Entry for a different user? */
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- if (strcmp(user, uent->ut_user))
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+ if (strncmp(user, uent->ut_user, UT_NAMESIZE))
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continue;
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sstrncpy(dev+5, uent->ut_line, PATH_MAX-5);
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if (stat(dev, &st) < 0)
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@@ -281,6 +283,7 @@ static void write_console_warning(struct quota_warning *warn)
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}
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}
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if (!max_atime) {
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+skip_utmp:
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/*
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* This can happen quite easily so don't spam syslog with
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* the error
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--
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2.13.6
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