On Thu, Aug 23, 2012 at 08:12:30AM -0400, J. Bruce Fields wrote: > On Thu, Aug 23, 2012 at 02:43:27PM +0400, Cyrill Gorcunov wrote: > > If there is no s_export_op present in a target superblock > > we might have nil dereference. > > Is that NULL dereference possible with current code, or is it a check > you're adding to account for a new caller that you're about to add? > > I believe it's the latter, but this would be a good thing to make clear > in the changelog. With the current code it seems to be impossible (well, i can't be sure about nfs caller) because do_sys_name_to_handle does check for s_export_op to exist. Updated changelog below. After all I think not checking s_export_op was a mistake in general -- this routine is exported to other modules but has no a single line of comment about possibility of nil dereference. --- From: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> Subject: fs, exportfs: Escape nil dereference if no s_export_op present This routine will be used to generate a file handle in fdinfo output for inotify subsystem, where if no s_export_op present the general export_encode_fh should be used. Thus add a test if s_export_op present inside exportfs_encode_fh itself. Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx> CC: Alexey Dobriyan <adobriyan@xxxxxxxxx> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> CC: James Bottomley <jbottomley@xxxxxxxxxxxxx> CC: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> CC: Alexey Dobriyan <adobriyan@xxxxxxxxx> CC: Matthew Helsley <matt.helsley@xxxxxxxxx> CC: "J. Bruce Fields" <bfields@xxxxxxxxxxxx> CC: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> --- fs/exportfs/expfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6.git/fs/exportfs/expfs.c =================================================================== --- linux-2.6.git.orig/fs/exportfs/expfs.c +++ linux-2.6.git/fs/exportfs/expfs.c @@ -357,7 +357,7 @@ int exportfs_encode_fh(struct dentry *de */ parent = p->d_inode; } - if (nop->encode_fh) + if (nop && nop->encode_fh) error = nop->encode_fh(inode, fid->raw, max_len, parent); else error = export_encode_fh(inode, fid, max_len, parent); -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
