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Kernel/Ext2: Avoid overflow when updating UID and GID values

Browse source 
Previously, attempting to update an ext2 inode with a UID or GID
larger than 65535 would overflow. We now write the high bits of UIDs
and GIDs to the same place that Linux does within the `osd2` struct.
This commit is contained in:
Tim Ledbetter 2023-10-01 16:41:12 +01:00 committed by Andreas Kling
parent 7e10f76021
commit db929e0fcf
Notes: sideshowbarker 2024-07-17 22:55:25 +09:00 
Author: https://github.com/tcl3
Commit: https://github.com/SerenityOS/serenity/commit/db929e0fcf
Pull-request: https://github.com/SerenityOS/serenity/pull/21288
5 changed files with 47 additions and 7 deletions
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6
Kernel/FileSystem/Ext2FS/FileSystem.cpp
View file

@ -510,8 +510,10 @@ ErrorOr<NonnullRefPtr<Inode>> Ext2FS::create_inode(Ext2FSInode& parent_inode, St
ext2_inode e2inode {};
auto now = kgettimeofday().truncated_seconds_since_epoch();
e2inode.i_mode = mode;
e2inode.i_uid = uid.value();
e2inode.i_gid = gid.value();
e2inode.i_uid = static_cast<u16>(uid.value());
ext2fs_set_i_uid_high(e2inode, uid.value() >> 16);
e2inode.i_gid = static_cast<u16>(gid.value());
ext2fs_set_i_gid_high(e2inode, gid.value() >> 16);
e2inode.i_size = 0;
e2inode.i_atime = now;
e2inode.i_ctime = now;

12
Kernel/FileSystem/Ext2FS/Inode.cpp
View file

@ -471,8 +471,8 @@ InodeMetadata Ext2FSInode::metadata() const
metadata.inode = identifier();
metadata.size = size();
metadata.mode = m_raw_inode.i_mode;
metadata.uid = m_raw_inode.i_uid;
metadata.gid = m_raw_inode.i_gid;
metadata.uid = inode_uid(m_raw_inode);
metadata.gid = inode_gid(m_raw_inode);
metadata.link_count = m_raw_inode.i_links_count;
metadata.atime = UnixDateTime::from_seconds_since_epoch(m_raw_inode.i_atime);
metadata.ctime = UnixDateTime::from_seconds_since_epoch(m_raw_inode.i_ctime);
@ -1051,10 +1051,12 @@ ErrorOr<void> Ext2FSInode::chmod(mode_t mode)
ErrorOr<void> Ext2FSInode::chown(UserID uid, GroupID gid)
{
MutexLocker locker(m_inode_lock);
if (m_raw_inode.i_uid == uid && m_raw_inode.i_gid == gid)
if (inode_uid(m_raw_inode) == uid && inode_gid(m_raw_inode) == gid)
return {};
m_raw_inode.i_uid = uid.value();
m_raw_inode.i_gid = gid.value();
m_raw_inode.i_uid = static_cast<u16>(uid.value());
ext2fs_set_i_uid_high(m_raw_inode, uid.value() >> 16);
m_raw_inode.i_gid = static_cast<u16>(gid.value());
ext2fs_set_i_gid_high(m_raw_inode, gid.value() >> 16);
set_metadata_dirty(true);
return {};
}

4
Meta/build-root-filesystem.sh
View file

@ -98,6 +98,10 @@ if [ -f mnt/bin/timezone ]; then
chown 0:$phys_gid mnt/bin/timezone
chmod 4750 mnt/bin/timezone
fi
if [ -f mnt/usr/Tests/Kernel/TestExt2FS ]; then
chown 0:0 mnt/usr/Tests/Kernel/TestExt2FS
chmod 4755 mnt/usr/Tests/Kernel/TestExt2FS
fi
if [ -f mnt/usr/Tests/Kernel/TestMemoryDeviceMmap ]; then
chown 0:0 mnt/usr/Tests/Kernel/TestMemoryDeviceMmap
chmod 4755 mnt/usr/Tests/Kernel/TestMemoryDeviceMmap

1
Tests/Kernel/CMakeLists.txt
View file

@ -40,6 +40,7 @@ serenity_test("crash.cpp" Kernel MAIN_ALREADY_DEFINED)
set(LIBTEST_BASED_SOURCES
TestEmptyPrivateInodeVMObject.cpp
TestEmptySharedInodeVMObject.cpp
TestExt2FS.cpp
TestInvalidUIDSet.cpp
TestSharedInodeVMObject.cpp
TestPosixFallocate.cpp

31
Tests/Kernel/TestExt2FS.cpp Normal file
View file

@ -0,0 +1,31 @@
/*
* Copyright (c) 2023, Tim Ledbetter <timledbetter@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibTest/TestCase.h>
#include <fcntl.h>
#include <unistd.h>
TEST_CASE(test_uid_and_gid_high_bits_are_set)
{
static constexpr auto TEST_FILE_PATH = "/home/anon/.ext2_test";
auto uid = geteuid();
EXPECT_EQ(uid, 0u);
auto fd = open(TEST_FILE_PATH, O_CREAT);
auto cleanup_guard = ScopeGuard([&] {
close(fd);
unlink(TEST_FILE_PATH);
});
EXPECT_EQ(setuid(0), 0);
EXPECT_EQ(fchown(fd, 65536, 65536), 0);
struct stat st;
EXPECT_EQ(fstat(fd, &st), 0);
EXPECT_EQ(st.st_uid, 65536u);
EXPECT_EQ(st.st_gid, 65536u);
}