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Kernel: Prevent unveil returning ENOENT with cpath permissions

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This addresses the issue first enountered in #3644. If a path is
first unveiled with "c" permissions, we should NOT return ENOENT
if the node does not exist on the disk, as the program will most
likely be creating it at a later time.
This commit is contained in:
Jesse Buhagiar 2020-11-05 18:12:23 +11:00 • committed by Andreas Kling
parent c5b26a0df8
commit 940380c986
1 changed files with 20 additions and 8 deletions
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28
Kernel/Syscalls/unveil.cpp
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@ -24,6 +24,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/LexicalPath.h>
#include <AK/StringView.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
@ -58,18 +59,11 @@ int Process::sys$unveil(Userspace<const Syscall::SC_unveil_params*> user_params)
if (path.value().is_empty() || path.value().characters()[0] != '/')
return -EINVAL;
auto custody_or_error = VFS::the().resolve_path_without_veil(path.value(), root_directory());
if (custody_or_error.is_error())
// FIXME Should this be EINVAL?
return custody_or_error.error();
auto& custody = custody_or_error.value();
auto new_unveiled_path = custody->absolute_path();
auto permissions = copy_string_from_user(params.permissions);
if (permissions.is_null())
return -EFAULT;
// Let's work out permissions first...
unsigned new_permissions = 0;
for (const char permission : permissions) {
switch (permission) {
@ -90,6 +84,24 @@ int Process::sys$unveil(Userspace<const Syscall::SC_unveil_params*> user_params)
}
}
// Now, let's try and resolve the path and obtain custody of the inode on the disk, and if not, bail out with
// the error from resolve_path_without_veil()
// However, if the user specified unveil() with "c" permissions, we don't set errno if ENOENT is encountered,
// because they most likely intend the program to create the file for them later on.
// If this case is encountered, the parent node of the path is returned and the custody of that inode is used instead.
RefPtr<Custody> parent_custody; // Parent inode in case of ENOENT
String new_unveiled_path;
auto custody_or_error = VFS::the().resolve_path_without_veil(path.value(), root_directory(), &parent_custody);
if (!custody_or_error.is_error()) {
new_unveiled_path = custody_or_error.value()->absolute_path();
} else if (custody_or_error.error() == -ENOENT && parent_custody && (new_permissions & UnveiledPath::Access::CreateOrRemove)) {
String basename = LexicalPath(path.value()).basename();
new_unveiled_path = String::formatted("{}/{}", parent_custody->absolute_path(), basename);
} else {
// FIXME Should this be EINVAL?
return custody_or_error.error();
}
for (auto& unveiled_path : m_unveiled_paths) {
if (unveiled_path.path == new_unveiled_path) {
if (new_permissions & ~unveiled_path.permissions)