[PATCH] preallocate result for glfs_realpath in vfs_glusterfs

[Michael Adam]

On 2016-10-21 at 11:46 +0530, Anoop C S wrote:
> On Fri, 2016-10-21 at 00:57 +0200, Michael Adam wrote:
> > Hi all,
> > 
> > due to a recent change in glusterfs
> > https://review.gluster.org/#/c/15332/ ,
> > it is now wrong to just free the result
> > of glfs_realpath(). This needs to be discussed,
> > but here is a patch that makes us indedpendent
> > of the allocation mechanism used by glfs_realpath()
> > by handing in a pre-malloced result string.
> > 
> > This is based on discussions I had with
> > Rajesh and Anoop today.
> > 
> > Reviews appreciated!
> > Rajesh/Anoop, please also confirm this approach!
> > 
> 
> I can confirm that with this patch smbd no longer segfaults while mounting the share via Windows,
> CIFS and smbclient.
> 
> Since glfs_realpath honours pre-allocated memory this would be the most favourable approach.

Thanks for confirming Anoop!

Rajesh further pointed out to me that the code should
free the pre-allocated string if glfs_realpath fails,
which is obviously true.

Attached find an updated version of the patch.

Cheers - Michael

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From 803506a0d74c0d69f44cb0c0643395b7c32c1b57 Mon Sep 17 00:00:00 2001
From: Michael Adam <obnox at samba.org>
Date: Fri, 21 Oct 2016 00:15:06 +0200
Subject: [PATCH] vfs:glusterfs: preallocate result for glfs_realpath

This makes us independent of the allocation
method used inside glfs_realpath.

Signed-off-by: Michael Adam <obnox at samba.org>
---
 source3/modules/vfs_glusterfs.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/source3/modules/vfs_glusterfs.c b/source3/modules/vfs_glusterfs.c
index 3e15ce6..1c9be2d 100644
--- a/source3/modules/vfs_glusterfs.c
+++ b/source3/modules/vfs_glusterfs.c
@@ -1140,7 +1140,20 @@ static int vfs_gluster_fallocate(struct vfs_handle_struct *handle,
 static char *vfs_gluster_realpath(struct vfs_handle_struct *handle,
 				  const char *path)
 {
-	return glfs_realpath(handle->data, path, 0);
+	char *result = NULL;
+	char *resolved_path = SMB_MALLOC_ARRAY(char, PATH_MAX+1);
+
+	if (resolved_path == NULL) {
+		errno = ENOMEM;
+		return NULL;
+	}
+
+	result = glfs_realpath(handle->data, path, resolved_path);
+	if (result == NULL) {
+		SAFE_FREE(resolved_path);
+	}
+
+	return result;
 }
 
 static bool vfs_gluster_lock(struct vfs_handle_struct *handle,
-- 
2.7.4

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