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make build_open_flags() treat O_CREAT | O_EXCL as implying O_NOFOLLOW

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O_CREAT | O_EXCL means "-EEXIST if we run into a trailing symlink".
As it is, we might or might not have LOOKUP_FOLLOW in op->intent
in that case - that depends upon having O_NOFOLLOW in open flags.
It doesn't matter, since we won't be checking it in that case -
do_last() bails out earlier.

However, making sure it's not set (i.e. acting as if we had an explicit
O_NOFOLLOW) makes the behaviour more explicit and allows to reorder the
check for O_CREAT | O_EXCL in do_last() with the call of step_into()
immediately following it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-01-08 20:19:38 -05:00
parent 1c9f5e06a6
commit 31d1726d72
2 changed files with 8 additions and 11 deletions
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15
fs/namei.c
View file

@ -3396,22 +3396,17 @@ static int do_last(struct nameidata *nd,
if (unlikely(error < 0))
return error;
/*
* create/update audit record if it already exists.
*/
audit_inode(nd->name, path.dentry, 0);
if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
path_to_nameidata(&path, nd);
return -EEXIST;
}
seq = 0; /* out of RCU mode, so the value doesn't matter */
inode = d_backing_inode(path.dentry);
finish_lookup:
error = step_into(nd, &path, 0, inode, seq);
if (unlikely(error))
return error;
if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
audit_inode(nd->name, nd->path.dentry, 0);
return -EEXIST;
}
finish_open:
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
error = complete_walk(nd);

4
fs/open.c
View file

@ -1049,8 +1049,10 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
if (flags & O_CREAT) {
op->intent |= LOOKUP_CREATE;
if (flags & O_EXCL)
if (flags & O_EXCL) {
op->intent |= LOOKUP_EXCL;
flags |= O_NOFOLLOW;
}
}
if (flags & O_DIRECTORY)