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From: Steven Whitehouse on 15 Jul 2010 10:30
From: Bob Peterson <rpeterso(a)redhat.com>

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(a)redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho(a)redhat.com>

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index b5612cb..f03afd9 100644
--- 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);
--
1.7.1.1

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