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do_fchownat(): import pathname only once

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Convert the user_path_at() call inside a retry loop into getname_flags() +
filename_lookup() + putname() and leave only filename_lookup() inside
the loop.

Since we have the default logics for use of LOOKUP_EMPTY (passed iff
AT_EMPTY_PATH is present in flags), just use getname_uflags() and
don't bother with setting LOOKUP_EMPTY in lookup_flags - getname_uflags()
will pass the right thing to getname_flags() and filename_lookup()
doesn't care about LOOKUP_EMPTY at all.

The things could be further simplified by use of cleanup.h stuff, but
let's not clutter the patch with that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2025-11-01 00:48:31 -04:00
commit 2e2d892fe9
1 changed files with 6 additions and 5 deletions
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11
fs/open.c
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@ -801,17 +801,17 @@ int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
int flag)
{
struct path path;
int error = -EINVAL;
int error;
int lookup_flags;
struct filename *name;
if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
goto out;
return -EINVAL;
lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
if (flag & AT_EMPTY_PATH)
lookup_flags |= LOOKUP_EMPTY;
name = getname_uflags(filename, flag);
retry:
error = user_path_at(dfd, filename, lookup_flags, &path);
error = filename_lookup(dfd, name, lookup_flags, &path, NULL);
if (error)
goto out;
error = mnt_want_write(path.mnt);
@ -826,6 +826,7 @@ out_release:
goto retry;
}
out:
putname(name);
return error;
}