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Kernel+LibC: Implement a few mount flags

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We now support these mount flags:
* MS_NODEV: disallow opening any devices from this file system
* MS_NOEXEC: disallow executing any executables from this file system
* MS_NOSUID: ignore set-user-id bits on executables from this file system

The fourth flag, MS_BIND, is defined, but currently ignored.
This commit is contained in:
Sergey Bugaev 2020-01-11 18:45:38 +03:00 • committed by Andreas Kling
parent 2fcbb846fb
commit 61c1106d9f
4 changed files with 19 additions and 5 deletions
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4
Kernel/FileSystem/VirtualFileSystem.cpp
View file

@ -216,11 +216,13 @@ KResultOr<NonnullRefPtr<FileDescription>> VFS::open(StringView path, int options
should_truncate_file = options & O_TRUNC;
}
if (options & O_EXEC) {
if (!metadata.may_execute(current->process()))
if (!metadata.may_execute(current->process()) || (custody.mount_flags() & MS_NOEXEC))
return KResult(-EACCES);
}
if (metadata.is_device()) {
if (custody.mount_flags() & MS_NODEV)
return KResult(-EACCES);
auto device = Device::get_device(metadata.major_device, metadata.minor_device);
if (device == nullptr) {
return KResult(-ENODEV);

5
Kernel/FileSystem/VirtualFileSystem.h
View file

@ -28,6 +28,11 @@
#define O_DIRECT 04000000
#define O_NOFOLLOW_NOERROR 0x4000000
#define MS_NODEV 1
#define MS_NOEXEC 2
#define MS_NOSUID 4
#define MS_BIND 8
class Custody;
class Device;
class FileDescription;

10
Kernel/Process.cpp
View file

@ -750,10 +750,12 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
// Copy of the master TLS region that we will clone for new threads
m_master_tls_region = master_tls_region;
if (metadata.is_setuid())
m_euid = metadata.uid;
if (metadata.is_setgid())
m_egid = metadata.gid;
if (!(description->custody()->mount_flags() & MS_NOSUID)) {
if (metadata.is_setuid())
m_euid = metadata.uid;
if (metadata.is_setgid())
m_egid = metadata.gid;
}
current->set_default_signal_dispositions();
current->m_signal_mask = 0;

5
Libraries/LibC/unistd.h
View file

@ -128,6 +128,11 @@ enum {
#define X_OK 1
#define F_OK 0
#define MS_NODEV 1
#define MS_NOEXEC 2
#define MS_NOSUID 4
#define MS_BIND 8
/*
* We aren't fully compliant (don't support policies, and don't have a wide
* range of values), but we do have process priorities.