On Thu, 2019-02-07 at 17:52 -0600, Benjamin Marzinski wrote:
> LOG_MSG() will dereference pp->mpp. Commit cb5ec664 added a call to
> LOG_MSG() before the check for (!pp->mpp) in check_path. This can
> cause
> multipathd to crash. LOG_MSG() should only be called if pp->mpp is
> set
> and a checker is selected.
>
> Also, checker_message() should fail to a generic message if c->cls
> isn't
> set (which means that a checker hasn't been selected).
>
> Fixes: cb5ec664 (multipathd: check_path: improve logging for
> "unusable
> path" case)
> Cc: Martin Wilck <mwilck@xxxxxxxx>
> Signed-off-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
Thanks a lot, but could we do the below instead? IMO it's better to
avoid similar errors in the future.
Martin
>From e5bef42f8f9d2aef9406873f515a45914c1aa251 Mon Sep 17 00:00:00 2001
From: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
Date: Thu, 7 Feb 2019 17:52:59 -0600
Subject: [PATCH] multipathd: avoid null pointer dereference in LOG_MSG
LOG_MSG() will dereference pp->mpp. Commit cb5ec664 added a call to
LOG_MSG() before the check for (!pp->mpp) in check_path. This can cause
multipathd to crash. LOG_MSG() should check the fields before dereferencing
them. Make checker_selected() an inline function to allow the compiler
to optimize away the usually redundant test "if (&checker->pp != NULL)".
Also, checker_message() should fail to a generic message if c->cls isn't
set (which means that a checker hasn't been selected).
Fixes: cb5ec664 (multipathd: check_path: improve logging for "unusable
path" case)
Signed-off-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
libmultipath/checkers.c | 9 +--------
libmultipath/checkers.h | 6 +++++-
multipathd/main.c | 6 ++++--
3 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/libmultipath/checkers.c b/libmultipath/checkers.c
index 848c4c34..f4fdcae9 100644
--- a/libmultipath/checkers.c
+++ b/libmultipath/checkers.c
@@ -261,13 +261,6 @@ int checker_check (struct checker * c, int path_state)
return r;
}
-int checker_selected(const struct checker *c)
-{
- if (!c)
- return 0;
- return c->cls != NULL;
-}
-
const char *checker_name(const struct checker *c)
{
if (!c || !c->cls)
@@ -295,7 +288,7 @@ const char *checker_message(const struct checker *c)
{
int id;
- if (!c || c->msgid < 0 ||
+ if (!c || !c->cls || c->msgid < 0 ||
(c->msgid >= CHECKER_GENERIC_MSGTABLE_SIZE &&
c->msgid < CHECKER_FIRST_MSGID))
goto bad_id;
diff --git a/libmultipath/checkers.h b/libmultipath/checkers.h
index b2e8f9aa..dab197f9 100644
--- a/libmultipath/checkers.h
+++ b/libmultipath/checkers.h
@@ -129,6 +129,11 @@ struct checker {
you want to stuff data in. */
};
+static inline int checker_selected(const struct checker *c)
+{
+ return c != NULL && c->cls != NULL;
+}
+
const char *checker_state_name(int);
int init_checkers(const char *);
void cleanup_checkers (void);
@@ -142,7 +147,6 @@ void checker_set_fd (struct checker *, int);
void checker_enable (struct checker *);
void checker_disable (struct checker *);
int checker_check (struct checker *, int);
-int checker_selected(const struct checker *);
int checker_is_sync(const struct checker *);
const char *checker_name (const struct checker *);
/*
diff --git a/multipathd/main.c b/multipathd/main.c
index d1a4f629..d1dd286c 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -92,7 +92,8 @@ static int use_watchdog;
#define LOG_MSG(lvl, verb, pp) \
do { \
- if (lvl <= verb) { \
+ if (pp->mpp && checker_selected(&pp->checker) && \
+ lvl <= verb) { \
if (pp->offline) \
condlog(lvl, "%s: %s - path offline", \
pp->mpp->alias, pp->dev); \
@@ -2017,7 +2018,8 @@ check_path (struct vectors * vecs, struct path * pp, int ticks)
}
if (newstate == PATH_WILD || newstate == PATH_UNCHECKED) {
- condlog(2, "%s: unusable path - checker failed", pp->dev);
+ condlog(2, "%s: unusable path (%s) - checker failed",
+ pp->dev, checker_state_name(newstate));
LOG_MSG(2, verbosity, pp);
conf = get_multipath_config();
pthread_cleanup_push(put_multipath_config, conf);
--
2.20.1
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