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Subject[patch 64/76] nfsd: fix oops on access from high-numbered ports
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: J. Bruce Fields <bfields@citi.umich.edu>

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>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
fs/nfsd/nfsfh.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -231,6 +231,7 @@ fh_verify(struct svc_rqst *rqstp, struct
fhp->fh_dentry = dentry;
fhp->fh_export = exp;
nfsd_nr_verified++;
+ cache_get(&exp->h);
} else {
/*
* just rechecking permissions
@@ -240,6 +241,7 @@ fh_verify(struct svc_rqst *rqstp, struct
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
@@ -251,8 +253,6 @@ fh_verify(struct svc_rqst *rqstp, struct
if (error)
goto out;
}
- cache_get(&exp->h);
-

error = nfsd_mode_check(rqstp, dentry->d_inode->i_mode, type);
if (error)
--


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