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Kernel: Make Inode::lookup() return a RefPtr<Inode>

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Previously this API would return an InodeIdentifier, which meant that
there was a race in path resolution where an inode could be unlinked
in between finding the InodeIdentifier for a path component, and
actually resolving that to an Inode object.

Attaching a test that would quickly trip an assertion before.

Test: Kernel/path-resolution-race.cpp
This commit is contained in:
Andreas Kling 2020-02-01 09:23:46 +01:00
parent 5aa37f6f5c
commit c44b4d61f3
11 changed files with 50 additions and 36 deletions
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12
Kernel/FileSystem/VirtualFileSystem.cpp
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@ -811,9 +811,8 @@ KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& ba
}
// Okay, let's look up this part.
auto child_id = parent.inode().lookup(part);
if (!child_id.is_valid()) {
auto child_inode = parent.inode().lookup(part);
if (!child_inode) {
if (out_parent) {
// ENOENT with a non-null parent custody signals to caller that
// we found the immediate parent of the file, but the file itself
@ -824,14 +823,13 @@ KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& ba
}
int mount_flags_for_child = parent.mount_flags();
// See if there's something mounted on the child; in that case
// we would need to return the guest inode, not the host inode.
if (auto mount = find_mount_for_host(child_id)) {
child_id = mount->guest();
if (auto mount = find_mount_for_host(child_inode->identifier())) {
child_inode = get_inode(mount->guest());
mount_flags_for_child = mount->flags();
}
auto child_inode = get_inode(child_id);
ASSERT(child_inode);
custody = Custody::create(&parent, part, *child_inode, mount_flags_for_child);