Fix kernel NULL pointer dereference by dlm_astd

Hi,

This patch replaces the one I previously posted here.

Regards,

Bob Peterson
Red Hat File Systems
--
commit 77ac19b0f0061396d0dc15f705ac4e0a574bd614

Author: Bob Peterson <[email protected]>
Date:   Thu Jun 17 15:38:32 2010 -0500

GFS2: Fix kernel NULL pointer dereference by dlm_astd

This patch fixes a problem in an error path when looking up dinodes. There are two sister-functions, gfs2_inode_lookup and gfs2_process_unlinked_inode. Both functions acquire and hold the i_iopen glock for the dinode being looked up. The last thing they try to do is hold the i_gl glock for the dinode. If that glock fails for some reason, the error path was incorrectly calling gfs2_glock_put for the i_iopen glock twice. This resulted in the glock being prematurely freed. The "minimum hold time" usually kept the glock in memory, but the lock interface to dlm (aka lock_dlm) freed its memory for the glock. In some circumstances, it would cause dlm's dlm_astd daemon to try to call the bast function for the freed lock_dlm memory, which resulted in a NULL pointer dereference.

rhbz#604244

fs/gfs2/inode.c +8 -4

index 4a1f236..21f901f 100644
@@ -171,7 +171,7 @@ struct inode *gfs2_inode_lookup(struct super_block *sb,
 {
 	struct inode *inode;
 	struct gfs2_inode *ip;
-	struct gfs2_glock *io_gl;
+	struct gfs2_glock *io_gl = NULL;
 	int error;
 
 	inode = gfs2_iget(sb, no_addr);

@@ -200,6 +200,7 @@ struct inode *gfs2_inode_lookup(struct super_block *sb,
 		ip->i_iopen_gh.gh_gl->gl_object = ip;
 
 		gfs2_glock_put(io_gl);
+		io_gl = NULL;
 
 		if ((type == DT_UNKNOWN) && (no_formal_ino == 0))
 			goto gfs2_nfsbypass;

@@ -230,7 +231,8 @@ gfs2_nfsbypass:
 fail_glock:
 	gfs2_glock_dq(&ip->i_iopen_gh);
 fail_iopen:
-	gfs2_glock_put(io_gl);
+	if (io_gl)
+		gfs2_glock_put(io_gl);
 fail_put:
 	if (inode->i_state & I_NEW)
 		ip->i_gl->gl_object = NULL;

@@ -258,7 +260,7 @@ void gfs2_process_unlinked_inode(struct super_block *sb, u64 no_addr)
 {
 	struct gfs2_sbd *sdp;
 	struct gfs2_inode *ip;
-	struct gfs2_glock *io_gl;
+	struct gfs2_glock *io_gl = NULL;
 	int error;
 	struct gfs2_holder gh;
 	struct inode *inode;

@@ -295,6 +297,7 @@ void gfs2_process_unlinked_inode(struct super_block *sb, u64 no_addr)
 
 	ip->i_iopen_gh.gh_gl->gl_object = ip;
 	gfs2_glock_put(io_gl);
+	io_gl = NULL;
 
 	inode->i_mode = DT2IF(DT_UNKNOWN);
 

@@ -321,7 +324,8 @@ void gfs2_process_unlinked_inode(struct super_block *sb, u64 no_addr)
 fail_glock:
 	gfs2_glock_dq(&ip->i_iopen_gh);
 fail_iopen:
-	gfs2_glock_put(io_gl);
+	if (io_gl)
+		gfs2_glock_put(io_gl);
 fail_put:
 	ip->i_gl->gl_object = NULL;
 	gfs2_glock_put(ip->i_gl);