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Re: [Cluster-devel] [PATCH GFS2] Fix kernel NULL pointer dereference by dlm_astd



Hi,

Now in the -nmw GFS2 tree. Thanks,

Steve.

On Tue, 2010-06-15 at 12:07 -0400, Bob Peterson wrote:
> Hi,
> 
> 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.
> 
> This problem was discovered while testing bugzilla bug #595397.
> 
> Regards,
> 
> Bob Peterson
> Red Hat GFS
> 
> Signed-off-by: Bob Peterson <rpeterso redhat com> 
> --
>  fs/gfs2/inode.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
> index b5612cb..43e06ff 100644
> --- a/fs/gfs2/inode.c
> +++ b/fs/gfs2/inode.c
> @@ -197,8 +197,6 @@ struct inode *gfs2_inode_lookup(struct super_block *sb,
>  			goto fail_iopen;
>  		ip->i_iopen_gh.gh_gl->gl_object = ip;
>  
> -		gfs2_glock_put(io_gl);
> -
>  		if ((type == DT_UNKNOWN) && (no_formal_ino == 0))
>  			goto gfs2_nfsbypass;
>  
> @@ -224,6 +222,8 @@ struct inode *gfs2_inode_lookup(struct super_block *sb,
>  	}
>  
>  gfs2_nfsbypass:
> +	gfs2_glock_put(io_gl);
> +
>  	return inode;
>  fail_glock:
>  	gfs2_glock_dq(&ip->i_iopen_gh);
> @@ -292,7 +292,6 @@ void gfs2_process_unlinked_inode(struct super_block *sb, u64 no_addr)
>  		goto fail_iopen;
>  
>  	ip->i_iopen_gh.gh_gl->gl_object = ip;
> -	gfs2_glock_put(io_gl);
>  
>  	inode->i_mode = DT2IF(DT_UNKNOWN);
>  
> @@ -310,6 +309,7 @@ void gfs2_process_unlinked_inode(struct super_block *sb, u64 no_addr)
>  
>  	/* Inode is now uptodate */
>  	gfs2_glock_dq_uninit(&gh);
> +	gfs2_glock_put(io_gl);
>  	gfs2_set_iop(inode);
>  
>  	/* The iput will cause it to be deleted. */


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