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Message-Id: <1541407968-31350-1-git-send-email-asmadeus@codewreck.org>
Date: Mon, 5 Nov 2018 09:52:48 +0100
From: Dominique Martinet <asmadeus@...ewreck.org>
To: unlisted-recipients:; (no To-header on input)
Cc: Dominique Martinet <dominique.martinet@....fr>,
Eric Van Hensbergen <ericvh@...il.com>,
Latchesar Ionkov <lucho@...kov.net>,
syzkaller-bugs@...glegroups.com,
v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH] 9p/net: put a lower bound on msize
From: Dominique Martinet <dominique.martinet@....fr>
If the requested msize is too small (either from command line argument
or from the server version reply), we won't get any work done.
If it's *really* too small, nothing will work, and this got caught by
syzbot recently (on a new kmem_cache_create_usercopy() call)
Just set a minimum msize to 4k in both code paths, until someone
complains they have a use-case for a smaller msize.
We need to check in both mount option and server reply individually
because the msize for the first version request would be unchecked
with just a global check on clnt->msize.
Reported-by: syzbot+0c1d61e4db7db94102ca@...kaller.appspotmail.com
Signed-off-by: Dominique Martinet <dominique.martinet@....fr>
Cc: Eric Van Hensbergen <ericvh@...il.com>
Cc: Latchesar Ionkov <lucho@...kov.net>
---
net/9p/client.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/net/9p/client.c b/net/9p/client.c
index 2c9a17b9b46b..b1163ebdc622 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -181,6 +181,12 @@ static int parse_opts(char *opts, struct p9_client *clnt)
ret = r;
continue;
}
+ if (r < 4096) {
+ p9_debug(P9_DEBUG_ERROR,
+ "msize should be at least 4k\n");
+ ret = -EINVAL;
+ continue;
+ }
clnt->msize = option;
break;
case Opt_trans:
@@ -983,10 +989,18 @@ static int p9_client_version(struct p9_client *c)
else if (!strncmp(version, "9P2000", 6))
c->proto_version = p9_proto_legacy;
else {
+ p9_debug(P9_DEBUG_ERROR,
+ "server returned an unknown version: %s\n", version);
err = -EREMOTEIO;
goto error;
}
+ if (msize < 4096) {
+ p9_debug(P9_DEBUG_ERROR,
+ "server returned a msize < 4096: %d\n", msize);
+ err = -EREMOTEIO;
+ goto error;
+ }
if (msize < c->msize)
c->msize = msize;
@@ -1043,6 +1057,13 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
if (clnt->msize > clnt->trans_mod->maxsize)
clnt->msize = clnt->trans_mod->maxsize;
+ if (clnt->msize < 4096) {
+ p9_debug(P9_DEBUG_ERROR,
+ "Please specify a msize of at least 4k\n");
+ err = -EINVAL;
+ goto free_client;
+ }
+
err = p9_client_version(clnt);
if (err)
goto close_trans;
--
2.19.1
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