nfsd: fix oops on access from high-numbered ports

This bug was always here, but before my commit 6fa02839bf9412e18e77
("recheck for secure ports in fh_verify"), it could only be triggered by
failure of a kmalloc().  After that commit it could be triggered by a
client making a request from a non-reserved port for access to an export
marked "secure".  (Exports are "secure" by default.)

The result is a struct svc_export with a reference count one too low,
resulting in likely oopses next time the export is accessed.

The reference counting here is not straightforward; a later patch will
clean up fh_verify().

Thanks to Lukas Hejtmanek for the bug report and followup.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Lukas Hejtmanek <xhejtman@ics.muni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 1eb771d79cca09a51326541dc76f3db3405f9245..3e6b3f41ee1f342918e6e3f57493f3c0ab21b033 100644 (file)
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -232,6 +232,7 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
                fhp->fh_dentry = dentry;
                fhp->fh_export = exp;
                nfsd_nr_verified++;
+               cache_get(&exp->h);
        } else {
                /*
                 * just rechecking permissions
@@ -241,6 +242,7 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
                dprintk("nfsd: fh_verify - just checking\n");
                dentry = fhp->fh_dentry;
                exp = fhp->fh_export;
+               cache_get(&exp->h);
                /*
                 * Set user creds for this exportpoint; necessary even
                 * in the "just checking" case because this may be a
@@ -252,8 +254,6 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access)
                if (error)
                        goto out;
        }
-       cache_get(&exp->h);
-
 
        error = nfsd_mode_check(rqstp, dentry->d_inode->i_mode, type);
        if (error)