In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
ALSA: seq: oss: Fix UAF at handling events with embedded SysEx data<\/p>\n
The OSS sequencer processes the input MIDI bytes into a sequencer
\nevent to be dispatched later (in snd_seq_oss_midi_putc() called from
\nsnd_seq_oss_process_event()). When it’s a SysEx data, the event
\nrecord contains data.ext.ptr pointer to the original SysEx bytes, and
\nthe referred data is copied into the pool afterwards at dispatching.
\nThe problem is that, if the sequencer port gets closed concurrently
\nbefore the dispatch, the OSS sequencer core also releases the
\nresources (in snd_seq_oss_midi_check_exit_port()), while the pending
\nevent may hold a stale pointer, eventually leading to a UAF at a later
\ndispatch.<\/p>\n
Fortunately, there is already a refcounting mechanism (snd_use_lock_t)
\nfor the OSS MIDI device access, and for addressing the issue above, we
\njust need to extend the refcount until the event gets dispatched.<\/p>\n
This patch extends snd_seq_oss_process_event() to give back the
\nrefcount object, which is in turn released after calling the sequencer
\ndispatcher with the given event in the caller side.<\/p>\n
According to the original report, KASAN report as below:<\/p>\n
KASAN slab-use-after-free in snd_seq_event_dup+0x40c\/0x470
\nRIP: 0033:0x7f2cb66a6340
\nRead of size 6
\nCall trace:
\n dump_stack_lvl+0x73\/0xb0 (?:?)
\n print_report+0xd1\/0x650 (?:?)
\n srso_alias_return_thunk+0x5\/0xfbef5 (?:?)
\n __virt_addr_valid+0x1a7\/0x340 (?:?)
\n kasan_complete_mode_report_info+0x64\/0x200 (?:?)
\n kasan_report+0xf7\/0x130 (?:?)
\n snd_seq_event_dup+0x40c\/0x470 (?:?)
\n kasan_check_range+0x10c\/0x1c0 (?:?)
\n __asan_memcpy+0x27\/0x70 (?:?)
\n snd_seq_event_dup+0x9\/0x470 (?:?)
\n snd_seq_client_enqueue_event+0x139\/0x240 (?:?)
\n _raw_spin_unlock_irqrestore+0x4b\/0x60 (?:?)
\n snd_seq_kernel_client_enqueue+0x102\/0x120 (?:?)
\n snd_seq_oss_write+0x416\/0x4e0 (?:?)
\n apparmor_file_permission+0x20\/0x30 (?:?)
\n odev_write+0x3b\/0x60 (?:?)
\n vfs_write+0x1ce\/0x850 (?:?)
\n lock_release+0xc8\/0x2a0 (?:?)
\n __kasan_check_write+0x18\/0x20 (?:?)
\n __mutex_unlock_slowpath+0x129\/0x510 (?:?)
\n ksys_write+0xe1\/0x180 (?:?)
\n mutex_unlock+0x16\/0x20 (?:?)
\n odev_ioctl+0x65\/0xc0 (?:?)
\n __x64_sys_write+0x46\/0x60 (?:?)
\n x64_sys_call+0x7d\/0x20d0 (?:?)
\n do_syscall_64+0xc1\/0x360 (arch\/x86\/entry\/syscall_64.c:87)
\n entry_SYSCALL_64_after_hwframe+0x77\/0x7f (?:?)<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
ALSA: seq: oss: Fix UAF at handling events with embedded SysEx data<\/p>\n
The OSS sequencer processes the input MIDI bytes into a sequen<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-7342","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/7342","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7342"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7342"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7342"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}