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From:   Trond Myklebust <trondmy@gmail.com>
To:     Steve Dickson <SteveD@redhat.com>
Cc:     "J. Bruce Fields" <bfields@redhat.com>, linux-nfs@vger.kernel.org
Subject: [PATCH 2/3] mountd: Ensure nfsd_path_strip_root() uses the canonicalised path
Date:   Mon,  3 Jun 2019 13:12:26 -0400
Message-Id: <20190603171227.29148-3-trond.myklebust@hammerspace.com>
In-Reply-To: <20190603171227.29148-2-trond.myklebust@hammerspace.com>
References: <20190603171227.29148-1-trond.myklebust@hammerspace.com>
 <20190603171227.29148-2-trond.myklebust@hammerspace.com>
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When attempting to strip the root path, we should first canonicalise
the root pathname.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 support/misc/nfsd_path.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/support/misc/nfsd_path.c b/support/misc/nfsd_path.c
index 2f41a793c534..9b38dd96007f 100644
--- a/support/misc/nfsd_path.c
+++ b/support/misc/nfsd_path.c
@@ -1,6 +1,7 @@
 #include <errno.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <limits.h>
 #include <stdlib.h>
 #include <unistd.h>
 
@@ -62,13 +63,21 @@ nfsd_path_nfsd_rootdir(void)
 char *
 nfsd_path_strip_root(char *pathname)
 {
+	char buffer[PATH_MAX];
 	const char *dir = nfsd_path_nfsd_rootdir();
 	char *ret;
 
-	ret = strstr(pathname, dir);
-	if (!ret || ret != pathname)
-		return pathname;
-	return pathname + strlen(dir);
+	if (!dir)
+		goto out;
+	if (realpath(dir, buffer)) {
+		ret = strstr(pathname, buffer);
+		if (ret == pathname)
+			return pathname + strlen(dir);
+	} else
+		xlog(D_GENERAL, "%s: failed to resolve path %s: %m",
+				__func__, dir);
+out:
+	return pathname;
 }
 
 char *
-- 
2.21.0