In the Linux kernel, the following vulnerability has been resolved:
USB: core: Make do_proc_control() and do_proc_bulk() killable
The USBDEVFS_CONTROL and USBDEVFS_BULK ioctls invoke
usb_start_wait_urb(), which contains an uninterruptible wait with a
user-specified timeout value. If timeout value is very large and the
device being accessed does not respond in a reasonable amount of time,
the kernel will complain about "Task X blocked for more than N
seconds", as found in testing by syzbot:
INFO: task syz-executor.0:8700 blocked for more than 143 seconds.
Not tainted 5.14.0-rc7-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0 state:D stack:23192 pid: 8700 ppid: 8455 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4681 [inline]
__schedule+0xc07/0x11f0 kernel/sched/core.c:5938
schedule+0x14b/0x210 kernel/sched/core.c:6017
schedule_timeout+0x98/0x2f0 kernel/time/timer.c:1857
do_wait_for_common+0x2da/0x480 kernel/sched/completion.c:85
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion_timeout+0x46/0x60 kernel/sched/completion.c:157
usb_start_wait_urb+0x167/0x550 drivers/usb/core/message.c:63
do_proc_bulk+0x978/0x1080 drivers/usb/core/devio.c:1236
proc_bulk drivers/usb/core/devio.c:1273 [inline]
usbdev_do_ioctl drivers/usb/core/devio.c:2547 [inline]
usbdev_ioctl+0x3441/0x6b10 drivers/usb/core/devio.c:2713
...
To fix this problem, this patch replaces usbfs's calls to
usb_control_msg() and usb_bulk_msg() with special-purpose code that
does essentially the same thing (as recommended in the comment for
usb_start_wait_urb()), except that it always uses a killable wait and
it uses GFP_KERNEL rather than GFP_NOIO.
In the Linux kernel, the following vulnerability has been resolved:
media: mxl111sf: change mutex_init() location
Syzbot reported, that mxl111sf_ctrl_msg() uses uninitialized
mutex. The problem was in wrong mutex_init() location.
Previous mutex_init(&state->msg_lock) call was in ->init() function, but
dvb_usbv2_init() has this order of calls:
dvb_usbv2_init()
dvb_usbv2_adapter_init()
dvb_usbv2_adapter_frontend_init()
props->frontend_attach()
props->init()
Since mxl111sf_* devices call mxl111sf_ctrl_msg() in ->frontend_attach()
internally we need to initialize state->msg_lock before
frontend_attach(). To achieve it, ->probe() call added to all mxl111sf_*
devices, which will simply initiaize mutex.
In the Linux kernel, the following vulnerability has been resolved:
m68k: Fix spinlock race in kernel thread creation
Context switching does take care to retain the correct lock owner across
the switch from 'prev' to 'next' tasks. This does rely on interrupts
remaining disabled for the entire duration of the switch.
This condition is guaranteed for normal process creation and context
switching between already running processes, because both 'prev' and
'next' already have interrupts disabled in their saved copies of the
status register.
The situation is different for newly created kernel threads. The status
register is set to PS_S in copy_thread(), which does leave the IPL at 0.
Upon restoring the 'next' thread's status register in switch_to() aka
resume(), interrupts then become enabled prematurely. resume() then
returns via ret_from_kernel_thread() and schedule_tail() where run queue
lock is released (see finish_task_switch() and finish_lock_switch()).
A timer interrupt calling scheduler_tick() before the lock is released
in finish_task_switch() will find the lock already taken, with the
current task as lock owner. This causes a spinlock recursion warning as
reported by Guenter Roeck.
As far as I can ascertain, this race has been opened in commit
533e6903bea0 ("m68k: split ret_from_fork(), simplify kernel_thread()")
but I haven't done a detailed study of kernel history so it may well
predate that commit.
Interrupts cannot be disabled in the saved status register copy for
kernel threads (init will complain about interrupts disabled when
finally starting user space). Disable interrupts temporarily when
switching the tasks' register sets in resume().
Note that a simple oriw 0x700,%sr after restoring sr is not enough here
- this leaves enough of a race for the 'spinlock recursion' warning to
still be observed.
Tested on ARAnyM and qemu (Quadra 800 emulation).
In the Linux kernel, the following vulnerability has been resolved:
ALSA: timer: Set lower bound of start tick time
Currently ALSA timer doesn't have the lower limit of the start tick
time, and it allows a very small size, e.g. 1 tick with 1ns resolution
for hrtimer. Such a situation may lead to an unexpected RCU stall,
where the callback repeatedly queuing the expire update, as reported
by fuzzer.
This patch introduces a sanity check of the timer start tick time, so
that the system returns an error when a too small start size is set.
As of this patch, the lower limit is hard-coded to 100us, which is
small enough but can still work somehow.
In the Linux kernel, the following vulnerability has been resolved:
ring-buffer: Fix a race between readers and resize checks
The reader code in rb_get_reader_page() swaps a new reader page into the
ring buffer by doing cmpxchg on old->list.prev->next to point it to the
new page. Following that, if the operation is successful,
old->list.next->prev gets updated too. This means the underlying
doubly-linked list is temporarily inconsistent, page->prev->next or
page->next->prev might not be equal back to page for some page in the
ring buffer.
The resize operation in ring_buffer_resize() can be invoked in parallel.
It calls rb_check_pages() which can detect the described inconsistency
and stop further tracing:
[ 190.271762] ------------[ cut here ]------------
[ 190.271771] WARNING: CPU: 1 PID: 6186 at kernel/trace/ring_buffer.c:1467 rb_check_pages.isra.0+0x6a/0xa0
[ 190.271789] Modules linked in: [...]
[ 190.271991] Unloaded tainted modules: intel_uncore_frequency(E):1 skx_edac(E):1
[ 190.272002] CPU: 1 PID: 6186 Comm: cmd.sh Kdump: loaded Tainted: G E 6.9.0-rc6-default #5 158d3e1e6d0b091c34c3b96bfd99a1c58306d79f
[ 190.272011] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552c-rebuilt.opensuse.org 04/01/2014
[ 190.272015] RIP: 0010:rb_check_pages.isra.0+0x6a/0xa0
[ 190.272023] Code: [...]
[ 190.272028] RSP: 0018:ffff9c37463abb70 EFLAGS: 00010206
[ 190.272034] RAX: ffff8eba04b6cb80 RBX: 0000000000000007 RCX: ffff8eba01f13d80
[ 190.272038] RDX: ffff8eba01f130c0 RSI: ffff8eba04b6cd00 RDI: ffff8eba0004c700
[ 190.272042] RBP: ffff8eba0004c700 R08: 0000000000010002 R09: 0000000000000000
[ 190.272045] R10: 00000000ffff7f52 R11: ffff8eba7f600000 R12: ffff8eba0004c720
[ 190.272049] R13: ffff8eba00223a00 R14: 0000000000000008 R15: ffff8eba067a8000
[ 190.272053] FS: 00007f1bd64752c0(0000) GS:ffff8eba7f680000(0000) knlGS:0000000000000000
[ 190.272057] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 190.272061] CR2: 00007f1bd6662590 CR3: 000000010291e001 CR4: 0000000000370ef0
[ 190.272070] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 190.272073] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 190.272077] Call Trace:
[ 190.272098] <TASK>
[ 190.272189] ring_buffer_resize+0x2ab/0x460
[ 190.272199] __tracing_resize_ring_buffer.part.0+0x23/0xa0
[ 190.272206] tracing_resize_ring_buffer+0x65/0x90
[ 190.272216] tracing_entries_write+0x74/0xc0
[ 190.272225] vfs_write+0xf5/0x420
[ 190.272248] ksys_write+0x67/0xe0
[ 190.272256] do_syscall_64+0x82/0x170
[ 190.272363] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 190.272373] RIP: 0033:0x7f1bd657d263
[ 190.272381] Code: [...]
[ 190.272385] RSP: 002b:00007ffe72b643f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 190.272391] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f1bd657d263
[ 190.272395] RDX: 0000000000000002 RSI: 0000555a6eb538e0 RDI: 0000000000000001
[ 190.272398] RBP: 0000555a6eb538e0 R08: 000000000000000a R09: 0000000000000000
[ 190.272401] R10: 0000555a6eb55190 R11: 0000000000000246 R12: 00007f1bd6662500
[ 190.272404] R13: 0000000000000002 R14: 00007f1bd6667c00 R15: 0000000000000002
[ 190.272412] </TASK>
[ 190.272414] ---[ end trace 0000000000000000 ]---
Note that ring_buffer_resize() calls rb_check_pages() only if the parent
trace_buffer has recording disabled. Recent commit d78ab792705c
("tracing: Stop current tracer when resizing buffer") causes that it is
now always the case which makes it more likely to experience this issue.
The window to hit this race is nonetheless very small. To help
reproducing it, one can add a delay loop in rb_get_reader_page():
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
if (!ret)
goto spin;
for (unsigned i = 0; i < 1U << 26; i++) /* inserted delay loop */
__asm__ __volatile__ ("" : : : "memory");
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
..
---truncated---
In the Linux kernel, the following vulnerability has been resolved:
macintosh/via-macii: Fix "BUG: sleeping function called from invalid context"
The via-macii ADB driver calls request_irq() after disabling hard
interrupts. But disabling interrupts isn't necessary here because the
VIA shift register interrupt was masked during VIA1 initialization.
In the Linux kernel, the following vulnerability has been resolved:
af_unix: Fix data races in unix_release_sock/unix_stream_sendmsg
A data-race condition has been identified in af_unix. In one data path,
the write function unix_release_sock() atomically writes to
sk->sk_shutdown using WRITE_ONCE. However, on the reader side,
unix_stream_sendmsg() does not read it atomically. Consequently, this
issue is causing the following KCSAN splat to occur:
BUG: KCSAN: data-race in unix_release_sock / unix_stream_sendmsg
write (marked) to 0xffff88867256ddbb of 1 bytes by task 7270 on cpu 28:
unix_release_sock (net/unix/af_unix.c:640)
unix_release (net/unix/af_unix.c:1050)
sock_close (net/socket.c:659 net/socket.c:1421)
__fput (fs/file_table.c:422)
__fput_sync (fs/file_table.c:508)
__se_sys_close (fs/open.c:1559 fs/open.c:1541)
__x64_sys_close (fs/open.c:1541)
x64_sys_call (arch/x86/entry/syscall_64.c:33)
do_syscall_64 (arch/x86/entry/common.c:?)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
read to 0xffff88867256ddbb of 1 bytes by task 989 on cpu 14:
unix_stream_sendmsg (net/unix/af_unix.c:2273)
__sock_sendmsg (net/socket.c:730 net/socket.c:745)
____sys_sendmsg (net/socket.c:2584)
__sys_sendmmsg (net/socket.c:2638 net/socket.c:2724)
__x64_sys_sendmmsg (net/socket.c:2753 net/socket.c:2750 net/socket.c:2750)
x64_sys_call (arch/x86/entry/syscall_64.c:33)
do_syscall_64 (arch/x86/entry/common.c:?)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
value changed: 0x01 -> 0x03
The line numbers are related to commit dd5a440a31fa ("Linux 6.9-rc7").
Commit e1d09c2c2f57 ("af_unix: Fix data races around sk->sk_shutdown.")
addressed a comparable issue in the past regarding sk->sk_shutdown.
However, it overlooked resolving this particular data path.
This patch only offending unix_stream_sendmsg() function, since the
other reads seem to be protected by unix_state_lock() as discussed in
In the Linux kernel, the following vulnerability has been resolved:
eth: sungem: remove .ndo_poll_controller to avoid deadlocks
Erhard reports netpoll warnings from sungem:
netpoll_send_skb_on_dev(): eth0 enabled interrupts in poll (gem_start_xmit+0x0/0x398)
WARNING: CPU: 1 PID: 1 at net/core/netpoll.c:370 netpoll_send_skb+0x1fc/0x20c
gem_poll_controller() disables interrupts, which may sleep.
We can't sleep in netpoll, it has interrupts disabled completely.
Strangely, gem_poll_controller() doesn't even poll the completions,
and instead acts as if an interrupt has fired so it just schedules
NAPI and exits. None of this has been necessary for years, since
netpoll invokes NAPI directly.
In the Linux kernel, the following vulnerability has been resolved:
jffs2: prevent xattr node from overflowing the eraseblock
Add a check to make sure that the requested xattr node size is no larger
than the eraseblock minus the cleanmarker.
Unlike the usual inode nodes, the xattr nodes aren't split into parts
and spread across multiple eraseblocks, which means that a xattr node
must not occupy more than one eraseblock. If the requested xattr value is
too large, the xattr node can spill onto the next eraseblock, overwriting
the nodes and causing errors such as:
jffs2: argh. node added in wrong place at 0x0000b050(2)
jffs2: nextblock 0x0000a000, expected at 0000b00c
jffs2: error: (823) do_verify_xattr_datum: node CRC failed at 0x01e050,
read=0xfc892c93, calc=0x000000
jffs2: notice: (823) jffs2_get_inode_nodes: Node header CRC failed
at 0x01e00c. {848f,2fc4,0fef511f,59a3d171}
jffs2: Node at 0x0000000c with length 0x00001044 would run over the
end of the erase block
jffs2: Perhaps the file system was created with the wrong erase size?
jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found
at 0x00000010: 0x1044 instead
This breaks the filesystem and can lead to KASAN crashes such as:
BUG: KASAN: slab-out-of-bounds in jffs2_sum_add_kvec+0x125e/0x15d0
Read of size 4 at addr ffff88802c31e914 by task repro/830
CPU: 0 PID: 830 Comm: repro Not tainted 6.9.0-rc3+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS Arch Linux 1.16.3-1-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xc6/0x120
print_report+0xc4/0x620
? __virt_addr_valid+0x308/0x5b0
kasan_report+0xc1/0xf0
? jffs2_sum_add_kvec+0x125e/0x15d0
? jffs2_sum_add_kvec+0x125e/0x15d0
jffs2_sum_add_kvec+0x125e/0x15d0
jffs2_flash_direct_writev+0xa8/0xd0
jffs2_flash_writev+0x9c9/0xef0
? __x64_sys_setxattr+0xc4/0x160
? do_syscall_64+0x69/0x140
? entry_SYSCALL_64_after_hwframe+0x76/0x7e
[...]
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.