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.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index b5612cbb62a51b75dc97699490658ce6939a4118..f03afd9c44bc748b51811bff46ccdab3d66fa619 100644 (file)
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -169,7 +169,7 @@ 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);
@@ -198,6 +198,7 @@ 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;
@@ -228,7 +229,8 @@ 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;
@@ -256,7 +258,7 @@ 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;
@@ -293,6 +295,7 @@ 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);
 
@@ -319,7 +322,8 @@ 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);