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minimal fix for do_filp_open() race 

failure exits on the no-O_CREAT side of do_filp_open() merge with
those of O_CREAT one; unfortunately, if do_path_lookup() returns
-ESTALE, we'll get out_filp:, notice that we are about to return
-ESTALE without having trying to create the sucker with LOOKUP_REVAL
and jump right into the O_CREAT side of code.  And proceed to try
and create a file.  Usually that'll fail with -ESTALE again, but
we can race and get that attempt of pathname resolution to succeed.

open() without O_CREAT really shouldn't end up creating files, races
or not.  The real fix is to rearchitect the whole do_filp_open(),
but for now splitting the failure exits will do.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2011-03-04 13:14:21 -05:00
parent b65a0e0c84
commit 1858efd471
1 changed files with 10 additions and 3 deletions
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13
fs/namei.c
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@ -2455,22 +2455,29 @@ struct file *do_filp_open(int dfd, const char *pathname,
/* !O_CREAT, simple open */
error = do_path_lookup(dfd, pathname, flags, &nd);
if (unlikely(error))
goto out_filp;
goto out_filp2;
error = -ELOOP;
if (!(nd.flags & LOOKUP_FOLLOW)) {
if (nd.inode->i_op->follow_link)
goto out_path;
goto out_path2;
}
error = -ENOTDIR;
if (nd.flags & LOOKUP_DIRECTORY) {
if (!nd.inode->i_op->lookup)
goto out_path;
goto out_path2;
}
audit_inode(pathname, nd.path.dentry);
filp = finish_open(&nd, open_flag, acc_mode);
out2:
release_open_intent(&nd);
return filp;
out_path2:
path_put(&nd.path);
out_filp2:
filp = ERR_PTR(error);
goto out2;
creat:
/* OK, have to create the file. Find the parent. */
error = path_init_rcu(dfd, pathname,