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NFS: Ensure we revalidate attributes before using execute_ok() 

Donald Buczek reports that NFS clients can also report incorrect
results for access() due to lack of revalidation of attributes
before calling execute_ok().
Looking closely, it seems chdir() is afflicted with the same problem.

Fix is to ensure we call nfs_revalidate_inode_rcu() or
nfs_revalidate_inode() as appropriate before deciding to trust
execute_ok().

Reported-by: Donald Buczek <buczek@molgen.mpg.de>
Link: http://lkml.kernel.org/r/1451331530-3748-1-git-send-email-buczek@molgen.mpg.de
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Trond Myklebust 2015-12-28 19:30:05 -05:00
parent 494f74a26c
commit 5c5fc09a11
1 changed files with 16 additions and 2 deletions
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18
fs/nfs/dir.c
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@ -2432,6 +2432,20 @@ int nfs_may_open(struct inode *inode, struct rpc_cred *cred, int openflags)
}
EXPORT_SYMBOL_GPL(nfs_may_open);
static int nfs_execute_ok(struct inode *inode, int mask)
{
struct nfs_server *server = NFS_SERVER(inode);
int ret;
if (mask & MAY_NOT_BLOCK)
ret = nfs_revalidate_inode_rcu(server, inode);
else
ret = nfs_revalidate_inode(server, inode);
if (ret == 0 && !execute_ok(inode))
ret = -EACCES;
return ret;
}
int nfs_permission(struct inode *inode, int mask)
{
struct rpc_cred *cred;
@ -2484,8 +2498,8 @@ int nfs_permission(struct inode *inode, int mask)
res = PTR_ERR(cred);
}
out:
if (!res && (mask & MAY_EXEC) && !execute_ok(inode))
res = -EACCES;
if (!res && (mask & MAY_EXEC))
res = nfs_execute_ok(inode, mask);
dfprintk(VFS, "NFS: permission(%s/%lu), mask=0x%x, res=%d\n",
inode->i_sb->s_id, inode->i_ino, mask, res);