[PATCH 3.12 056/182] NFSv4: Fix a use-after-free problem in open()

Jiri Slaby
2014-05-13T09:59:59Z

From: Trond Myklebust <trond.myklebust@primarydata.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit e911b8158ee1def8153849b1641b736026b036e0 upstream.

If we interrupt the nfs4_wait_for_completion_rpc_task() call in
nfs4_run_open_task(), then we don't prevent the RPC call from
completing. So freeing up the opendata->f_attr.mdsthreshold
in the error path in _nfs4_do_open() leads to a use-after-free
when the XDR decoder tries to decode the mdsthreshold information
from the server.

Fixes: 82be417aa37c0 (NFSv4.1 cache mdsthreshold values on OPEN)
Tested-by: Steve Dickson <SteveD@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
fs/nfs/nfs4proc.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index bcd42fbc04e7..40062e42c955 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1064,6 +1064,7 @@ static void nfs4_opendata_free(struct kref *kref)
dput(p->dentry);
nfs_sb_deactive(sb);
nfs_fattr_free_names(&p->f_attr);
+ kfree(p->f_attr.mdsthreshold);
kfree(p);
}

@@ -2236,10 +2237,12 @@ static int _nfs4_do_open(struct inode *dir,
}
}

- if (ctx_th && server->attr_bitmask[2] & FATTR4_WORD2_MDSTHRESHOLD) {
- opendata->f_attr.mdsthreshold = pnfs_mdsthreshold_alloc();
- if (!opendata->f_attr.mdsthreshold)
- goto err_free_label;
+ if (server->attr_bitmask[2] & FATTR4_WORD2_MDSTHRESHOLD) {
+ if (!opendata->f_attr.mdsthreshold) {
+ opendata->f_attr.mdsthreshold = pnfs_mdsthreshold_alloc();
+ if (!opendata->f_attr.mdsthreshold)
+ goto err_free_label;
+ }
opendata->o_arg.open_bitmap = &nfs4_pnfs_open_bitmap[0];
}
if (dentry->d_inode != NULL)
@@ -2267,11 +2270,10 @@ static int _nfs4_do_open(struct inode *dir,
if (opendata->file_created)
*opened |= FILE_CREATED;

- if (pnfs_use_threshold(ctx_th, opendata->f_attr.mdsthreshold, server))
+ if (pnfs_use_threshold(ctx_th, opendata->f_attr.mdsthreshold, server)) {
*ctx_th = opendata->f_attr.mdsthreshold;
- else
- kfree(opendata->f_attr.mdsthreshold);
- opendata->f_attr.mdsthreshold = NULL;
+ opendata->f_attr.mdsthreshold = NULL;
+ }

nfs4_label_free(olabel);

@@ -2281,7 +2283,6 @@ static int _nfs4_do_open(struct inode *dir,
err_free_label:
nfs4_label_free(olabel);
err_opendata_put:
- kfree(opendata->f_attr.mdsthreshold);
nfs4_opendata_put(opendata);
err_put_state_owner:
nfs4_put_state_owner(sp);
--
1.9.3