[PATCH 3.2 74/94] NFS: Fix another OPEN_DOWNGRADE bug

From: Ben Hutchings
Date: Sun Aug 14 2016 - 08:08:45 EST


3.2.82-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>

commit e547f2628327fec6afd2e03b46f113f614cca05b upstream.

Olga Kornievskaia reports that the following test fails to trigger
an OPEN_DOWNGRADE on the wire, and only triggers the final CLOSE.

fd0 = open(foo, RDRW) -- should be open on the wire for "both"
fd1 = open(foo, RDONLY) -- should be open on the wire for "read"
close(fd0) -- should trigger an open_downgrade
read(fd1)
close(fd1)

The issue is that we're missing a check for whether or not the current
state transitioned from an O_RDWR state as opposed to having transitioned
from a combination of O_RDONLY and O_WRONLY.

Reported-by: Olga Kornievskaia <aglo@xxxxxxxxx>
Fixes: cd9288ffaea4 ("NFSv4: Fix another bug in the close/open_downgrade code")
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2025,12 +2025,11 @@ static void nfs4_close_prepare(struct rp
call_close |= is_wronly;
else if (is_wronly)
calldata->arg.fmode |= FMODE_WRITE;
+ if (calldata->arg.fmode != (FMODE_READ|FMODE_WRITE))
+ call_close |= is_rdwr;
} else if (is_rdwr)
calldata->arg.fmode |= FMODE_READ|FMODE_WRITE;

- if (calldata->arg.fmode == 0)
- call_close |= is_rdwr;
-
spin_unlock(&state->owner->so_lock);

if (!call_close) {