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getname_flags() massage, part 1

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In case of long name don't reread what we'd already copied.
memmove() it instead.  That avoids the possibility of ending
up with empty name there and the need to look at the flags
on the slow path.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2025-11-19 17:15:23 -05:00
parent ca2a04e84a
commit 8ba29c85e2
1 changed files with 16 additions and 17 deletions
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33
fs/namei.c
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@ -174,36 +174,35 @@ getname_flags(const char __user *filename, int flags)
*/
if (unlikely(len == EMBEDDED_NAME_MAX)) {
const size_t size = offsetof(struct filename, iname[1]);
kname = (char *)result;
struct filename *p;
/*
* size is chosen that way we to guarantee that
* result->iname[0] is within the same object and that
* kname can't be equal to result->iname, no matter what.
*/
result = kzalloc(size, GFP_KERNEL);
if (unlikely(!result)) {
__putname(kname);
p = kzalloc(size, GFP_KERNEL);
if (unlikely(!p)) {
__putname(result);
return ERR_PTR(-ENOMEM);
}
result->name = kname;
len = strncpy_from_user(kname, filename, PATH_MAX);
memmove(result, &result->iname, EMBEDDED_NAME_MAX);
kname = (char *)result;
p->name = kname;
len = strncpy_from_user(kname + EMBEDDED_NAME_MAX,
filename + EMBEDDED_NAME_MAX,
PATH_MAX - EMBEDDED_NAME_MAX);
if (unlikely(len < 0)) {
__putname(kname);
kfree(result);
kfree(p);
__putname(result);
return ERR_PTR(len);
}
/* The empty path is special. */
if (unlikely(!len) && !(flags & LOOKUP_EMPTY)) {
__putname(kname);
kfree(result);
return ERR_PTR(-ENOENT);
}
if (unlikely(len == PATH_MAX)) {
__putname(kname);
kfree(result);
if (unlikely(len == PATH_MAX - EMBEDDED_NAME_MAX)) {
kfree(p);
__putname(result);
return ERR_PTR(-ENAMETOOLONG);
}
result = p;
}
initname(result);
audit_getname(result);