| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| This vulnerability affects Firefox < 143, Firefox ESR < 140.3, Thunderbird < 143, and Thunderbird < 140.3. |
| This vulnerability affects Firefox < 143 and Thunderbird < 143. |
| In the Linux kernel, the following vulnerability has been resolved:
ARM: 9170/1: fix panic when kasan and kprobe are enabled
arm32 uses software to simulate the instruction replaced
by kprobe. some instructions may be simulated by constructing
assembly functions. therefore, before executing instruction
simulation, it is necessary to construct assembly function
execution environment in C language through binding registers.
after kasan is enabled, the register binding relationship will
be destroyed, resulting in instruction simulation errors and
causing kernel panic.
the kprobe emulate instruction function is distributed in three
files: actions-common.c actions-arm.c actions-thumb.c, so disable
KASAN when compiling these files.
for example, use kprobe insert on cap_capable+20 after kasan
enabled, the cap_capable assembly code is as follows:
<cap_capable>:
e92d47f0 push {r4, r5, r6, r7, r8, r9, sl, lr}
e1a05000 mov r5, r0
e280006c add r0, r0, #108 ; 0x6c
e1a04001 mov r4, r1
e1a06002 mov r6, r2
e59fa090 ldr sl, [pc, #144] ;
ebfc7bf8 bl c03aa4b4 <__asan_load4>
e595706c ldr r7, [r5, #108] ; 0x6c
e2859014 add r9, r5, #20
......
The emulate_ldr assembly code after enabling kasan is as follows:
c06f1384 <emulate_ldr>:
e92d47f0 push {r4, r5, r6, r7, r8, r9, sl, lr}
e282803c add r8, r2, #60 ; 0x3c
e1a05000 mov r5, r0
e7e37855 ubfx r7, r5, #16, #4
e1a00008 mov r0, r8
e1a09001 mov r9, r1
e1a04002 mov r4, r2
ebf35462 bl c03c6530 <__asan_load4>
e357000f cmp r7, #15
e7e36655 ubfx r6, r5, #12, #4
e205a00f and sl, r5, #15
0a000001 beq c06f13bc <emulate_ldr+0x38>
e0840107 add r0, r4, r7, lsl #2
ebf3545c bl c03c6530 <__asan_load4>
e084010a add r0, r4, sl, lsl #2
ebf3545a bl c03c6530 <__asan_load4>
e2890010 add r0, r9, #16
ebf35458 bl c03c6530 <__asan_load4>
e5990010 ldr r0, [r9, #16]
e12fff30 blx r0
e356000f cm r6, #15
1a000014 bne c06f1430 <emulate_ldr+0xac>
e1a06000 mov r6, r0
e2840040 add r0, r4, #64 ; 0x40
......
when running in emulate_ldr to simulate the ldr instruction, panic
occurred, and the log is as follows:
Unable to handle kernel NULL pointer dereference at virtual address
00000090
pgd = ecb46400
[00000090] *pgd=2e0fa003, *pmd=00000000
Internal error: Oops: 206 [#1] SMP ARM
PC is at cap_capable+0x14/0xb0
LR is at emulate_ldr+0x50/0xc0
psr: 600d0293 sp : ecd63af8 ip : 00000004 fp : c0a7c30c
r10: 00000000 r9 : c30897f4 r8 : ecd63cd4
r7 : 0000000f r6 : 0000000a r5 : e59fa090 r4 : ecd63c98
r3 : c06ae294 r2 : 00000000 r1 : b7611300 r0 : bf4ec008
Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user
Control: 32c5387d Table: 2d546400 DAC: 55555555
Process bash (pid: 1643, stack limit = 0xecd60190)
(cap_capable) from (kprobe_handler+0x218/0x340)
(kprobe_handler) from (kprobe_trap_handler+0x24/0x48)
(kprobe_trap_handler) from (do_undefinstr+0x13c/0x364)
(do_undefinstr) from (__und_svc_finish+0x0/0x30)
(__und_svc_finish) from (cap_capable+0x18/0xb0)
(cap_capable) from (cap_vm_enough_memory+0x38/0x48)
(cap_vm_enough_memory) from
(security_vm_enough_memory_mm+0x48/0x6c)
(security_vm_enough_memory_mm) from
(copy_process.constprop.5+0x16b4/0x25c8)
(copy_process.constprop.5) from (_do_fork+0xe8/0x55c)
(_do_fork) from (SyS_clone+0x1c/0x24)
(SyS_clone) from (__sys_trace_return+0x0/0x10)
Code: 0050a0e1 6c0080e2 0140a0e1 0260a0e1 (f801f0e7) |
| 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:
drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()
Patch series "mm: follow_pte() improvements and acrn follow_pte() fixes".
Patch #1 fixes a bunch of issues I spotted in the acrn driver. It
compiles, that's all I know. I'll appreciate some review and testing from
acrn folks.
Patch #2+#3 improve follow_pte(), passing a VMA instead of the MM, adding
more sanity checks, and improving the documentation. Gave it a quick test
on x86-64 using VM_PAT that ends up using follow_pte().
This patch (of 3):
We currently miss handling various cases, resulting in a dangerous
follow_pte() (previously follow_pfn()) usage.
(1) We're not checking PTE write permissions.
Maybe we should simply always require pte_write() like we do for
pin_user_pages_fast(FOLL_WRITE)? Hard to tell, so let's check for
ACRN_MEM_ACCESS_WRITE for now.
(2) We're not rejecting refcounted pages.
As we are not using MMU notifiers, messing with refcounted pages is
dangerous and can result in use-after-free. Let's make sure to reject them.
(3) We are only looking at the first PTE of a bigger range.
We only lookup a single PTE, but memmap->len may span a larger area.
Let's loop over all involved PTEs and make sure the PFN range is
actually contiguous. Reject everything else: it couldn't have worked
either way, and rather made use access PFNs we shouldn't be accessing. |
| In the Linux kernel, the following vulnerability has been resolved:
nilfs2: fix potential kernel bug due to lack of writeback flag waiting
Destructive writes to a block device on which nilfs2 is mounted can cause
a kernel bug in the folio/page writeback start routine or writeback end
routine (__folio_start_writeback in the log below):
kernel BUG at mm/page-writeback.c:3070!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
...
RIP: 0010:__folio_start_writeback+0xbaa/0x10e0
Code: 25 ff 0f 00 00 0f 84 18 01 00 00 e8 40 ca c6 ff e9 17 f6 ff ff
e8 36 ca c6 ff 4c 89 f7 48 c7 c6 80 c0 12 84 e8 e7 b3 0f 00 90 <0f>
0b e8 1f ca c6 ff 4c 89 f7 48 c7 c6 a0 c6 12 84 e8 d0 b3 0f 00
...
Call Trace:
<TASK>
nilfs_segctor_do_construct+0x4654/0x69d0 [nilfs2]
nilfs_segctor_construct+0x181/0x6b0 [nilfs2]
nilfs_segctor_thread+0x548/0x11c0 [nilfs2]
kthread+0x2f0/0x390
ret_from_fork+0x4b/0x80
ret_from_fork_asm+0x1a/0x30
</TASK>
This is because when the log writer starts a writeback for segment summary
blocks or a super root block that use the backing device's page cache, it
does not wait for the ongoing folio/page writeback, resulting in an
inconsistent writeback state.
Fix this issue by waiting for ongoing writebacks when putting
folios/pages on the backing device into writeback state. |
| In the Linux kernel, the following vulnerability has been resolved:
media: ti: j721e-csi2rx: Fix races while restarting DMA
After the frame is submitted to DMA, it may happen that the submitted
list is not updated soon enough, and the DMA callback is triggered
before that.
This can lead to kernel crashes, so move everything in a single
lock/unlock section to prevent such races. |
| In the Linux kernel, the following vulnerability has been resolved:
dma-mapping: benchmark: fix node id validation
While validating node ids in map_benchmark_ioctl(), node_possible() may
be provided with invalid argument outside of [0,MAX_NUMNODES-1] range
leading to:
BUG: KASAN: wild-memory-access in map_benchmark_ioctl (kernel/dma/map_benchmark.c:214)
Read of size 8 at addr 1fffffff8ccb6398 by task dma_map_benchma/971
CPU: 7 PID: 971 Comm: dma_map_benchma Not tainted 6.9.0-rc6 #37
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:117)
kasan_report (mm/kasan/report.c:603)
kasan_check_range (mm/kasan/generic.c:189)
variable_test_bit (arch/x86/include/asm/bitops.h:227) [inline]
arch_test_bit (arch/x86/include/asm/bitops.h:239) [inline]
_test_bit at (include/asm-generic/bitops/instrumented-non-atomic.h:142) [inline]
node_state (include/linux/nodemask.h:423) [inline]
map_benchmark_ioctl (kernel/dma/map_benchmark.c:214)
full_proxy_unlocked_ioctl (fs/debugfs/file.c:333)
__x64_sys_ioctl (fs/ioctl.c:890)
do_syscall_64 (arch/x86/entry/common.c:83)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
Compare node ids with sane bounds first. NUMA_NO_NODE is considered a
special valid case meaning that benchmarking kthreads won't be bound to a
cpuset of a given node.
Found by Linux Verification Center (linuxtesting.org). |
| A security flaw has been discovered in yangzongzhuan RuoYi up to 4.8.1. This impacts the function filterKeyword of the file /com/ruoyi/common/utils/sql/SqlUtil.java of the component Blacklist Handler. The manipulation results in sql injection. The attack may be launched remotely. The exploit has been released to the public and may be exploited. |
| In the Linux kernel, the following vulnerability has been resolved:
greybus: lights: check return of get_channel_from_mode
If channel for the given node is not found we return null from
get_channel_from_mode. Make sure we validate the return pointer
before using it in two of the missing places.
This was originally reported in [0]:
Found by Linux Verification Center (linuxtesting.org) with SVACE.
[0] https://lore.kernel.org/all/20240301190425.120605-1-m.lobanov@rosalinux.ru |
| In the Linux kernel, the following vulnerability has been resolved:
soundwire: cadence: fix invalid PDI offset
For some reason, we add an offset to the PDI, presumably to skip the
PDI0 and PDI1 which are reserved for BPT.
This code is however completely wrong and leads to an out-of-bounds
access. We were just lucky so far since we used only a couple of PDIs
and remained within the PDI array bounds.
A Fixes: tag is not provided since there are no known platforms where
the out-of-bounds would be accessed, and the initial code had problems
as well.
A follow-up patch completely removes this useless offset. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/msm/dpu: Add callback function pointer check before its call
In dpu_core_irq_callback_handler() callback function pointer is compared to NULL,
but then callback function is unconditionally called by this pointer.
Fix this bug by adding conditional return.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Patchwork: https://patchwork.freedesktop.org/patch/588237/ |
| In the Linux kernel, the following vulnerability has been resolved:
media: stk1160: fix bounds checking in stk1160_copy_video()
The subtract in this condition is reversed. The ->length is the length
of the buffer. The ->bytesused is how many bytes we have copied thus
far. When the condition is reversed that means the result of the
subtraction is always negative but since it's unsigned then the result
is a very high positive value. That means the overflow check is never
true.
Additionally, the ->bytesused doesn't actually work for this purpose
because we're not writing to "buf->mem + buf->bytesused". Instead, the
math to calculate the destination where we are writing is a bit
involved. You calculate the number of full lines already written,
multiply by two, skip a line if necessary so that we start on an odd
numbered line, and add the offset into the line.
To fix this buffer overflow, just take the actual destination where we
are writing, if the offset is already out of bounds print an error and
return. Otherwise, write up to buf->length bytes. |
| A vulnerability was determined in itsourcecode Baptism Information Management System 1.0. Affected is an unknown function of the file /listbaptism.php. This manipulation of the argument bapt_id causes sql injection. It is possible to initiate the attack remotely. The exploit has been publicly disclosed and may be utilized. |
| A vulnerability was identified in SourceCodester Student Grading System 1.0. Affected by this vulnerability is an unknown functionality of the file /view_user.php. Such manipulation of the argument ID leads to sql injection. It is possible to launch the attack remotely. The exploit is publicly available and might be used. |
| In the Linux kernel, the following vulnerability has been resolved:
tcp: Fix shift-out-of-bounds in dctcp_update_alpha().
In dctcp_update_alpha(), we use a module parameter dctcp_shift_g
as follows:
alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g);
...
delivered_ce <<= (10 - dctcp_shift_g);
It seems syzkaller started fuzzing module parameters and triggered
shift-out-of-bounds [0] by setting 100 to dctcp_shift_g:
memcpy((void*)0x20000080,
"/sys/module/tcp_dctcp/parameters/dctcp_shift_g\000", 47);
res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x20000080ul,
/*flags=*/2ul, /*mode=*/0ul);
memcpy((void*)0x20000000, "100\000", 4);
syscall(__NR_write, /*fd=*/r[0], /*val=*/0x20000000ul, /*len=*/4ul);
Let's limit the max value of dctcp_shift_g by param_set_uint_minmax().
With this patch:
# echo 10 > /sys/module/tcp_dctcp/parameters/dctcp_shift_g
# cat /sys/module/tcp_dctcp/parameters/dctcp_shift_g
10
# echo 11 > /sys/module/tcp_dctcp/parameters/dctcp_shift_g
-bash: echo: write error: Invalid argument
[0]:
UBSAN: shift-out-of-bounds in net/ipv4/tcp_dctcp.c:143:12
shift exponent 100 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 0 PID: 8083 Comm: syz-executor345 Not tainted 6.9.0-05151-g1b294a1f3561 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x201/0x300 lib/dump_stack.c:114
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_shift_out_of_bounds+0x346/0x3a0 lib/ubsan.c:468
dctcp_update_alpha+0x540/0x570 net/ipv4/tcp_dctcp.c:143
tcp_in_ack_event net/ipv4/tcp_input.c:3802 [inline]
tcp_ack+0x17b1/0x3bc0 net/ipv4/tcp_input.c:3948
tcp_rcv_state_process+0x57a/0x2290 net/ipv4/tcp_input.c:6711
tcp_v4_do_rcv+0x764/0xc40 net/ipv4/tcp_ipv4.c:1937
sk_backlog_rcv include/net/sock.h:1106 [inline]
__release_sock+0x20f/0x350 net/core/sock.c:2983
release_sock+0x61/0x1f0 net/core/sock.c:3549
mptcp_subflow_shutdown+0x3d0/0x620 net/mptcp/protocol.c:2907
mptcp_check_send_data_fin+0x225/0x410 net/mptcp/protocol.c:2976
__mptcp_close+0x238/0xad0 net/mptcp/protocol.c:3072
mptcp_close+0x2a/0x1a0 net/mptcp/protocol.c:3127
inet_release+0x190/0x1f0 net/ipv4/af_inet.c:437
__sock_release net/socket.c:659 [inline]
sock_close+0xc0/0x240 net/socket.c:1421
__fput+0x41b/0x890 fs/file_table.c:422
task_work_run+0x23b/0x300 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x9c8/0x2540 kernel/exit.c:878
do_group_exit+0x201/0x2b0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xe4/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x67/0x6f
RIP: 0033:0x7f6c2b5005b6
Code: Unable to access opcode bytes at 0x7f6c2b50058c.
RSP: 002b:00007ffe883eb948 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f6c2b5862f0 RCX: 00007f6c2b5005b6
RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001
RBP: 0000000000000001 R08: 00000000000000e7 R09: ffffffffffffffc0
R10: 0000000000000006 R11: 0000000000000246 R12: 00007f6c2b5862f0
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
</TASK> |
| A security flaw has been discovered in SourceCodester Student Grading System 1.0. Affected by this issue is some unknown functionality of the file /edit_user.php. Performing manipulation of the argument ID results in sql injection. The attack can be initiated remotely. The exploit has been released to the public and may be exploited. |
| A weakness has been identified in SourceCodester Student Grading System 1.0. This affects an unknown part of the file /rms.php?page=users. Executing manipulation of the argument fname can lead to sql injection. The attack can be launched remotely. The exploit has been made available to the public and could be exploited. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: Forcibly leave nested virt when SMM state is toggled
Forcibly leave nested virtualization operation if userspace toggles SMM
state via KVM_SET_VCPU_EVENTS or KVM_SYNC_X86_EVENTS. If userspace
forces the vCPU out of SMM while it's post-VMXON and then injects an SMI,
vmx_enter_smm() will overwrite vmx->nested.smm.vmxon and end up with both
vmxon=false and smm.vmxon=false, but all other nVMX state allocated.
Don't attempt to gracefully handle the transition as (a) most transitions
are nonsencial, e.g. forcing SMM while L2 is running, (b) there isn't
sufficient information to handle all transitions, e.g. SVM wants access
to the SMRAM save state, and (c) KVM_SET_VCPU_EVENTS must precede
KVM_SET_NESTED_STATE during state restore as the latter disallows putting
the vCPU into L2 if SMM is active, and disallows tagging the vCPU as
being post-VMXON in SMM if SMM is not active.
Abuse of KVM_SET_VCPU_EVENTS manifests as a WARN and memory leak in nVMX
due to failure to free vmcs01's shadow VMCS, but the bug goes far beyond
just a memory leak, e.g. toggling SMM on while L2 is active puts the vCPU
in an architecturally impossible state.
WARNING: CPU: 0 PID: 3606 at free_loaded_vmcs arch/x86/kvm/vmx/vmx.c:2665 [inline]
WARNING: CPU: 0 PID: 3606 at free_loaded_vmcs+0x158/0x1a0 arch/x86/kvm/vmx/vmx.c:2656
Modules linked in:
CPU: 1 PID: 3606 Comm: syz-executor725 Not tainted 5.17.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:free_loaded_vmcs arch/x86/kvm/vmx/vmx.c:2665 [inline]
RIP: 0010:free_loaded_vmcs+0x158/0x1a0 arch/x86/kvm/vmx/vmx.c:2656
Code: <0f> 0b eb b3 e8 8f 4d 9f 00 e9 f7 fe ff ff 48 89 df e8 92 4d 9f 00
Call Trace:
<TASK>
kvm_arch_vcpu_destroy+0x72/0x2f0 arch/x86/kvm/x86.c:11123
kvm_vcpu_destroy arch/x86/kvm/../../../virt/kvm/kvm_main.c:441 [inline]
kvm_destroy_vcpus+0x11f/0x290 arch/x86/kvm/../../../virt/kvm/kvm_main.c:460
kvm_free_vcpus arch/x86/kvm/x86.c:11564 [inline]
kvm_arch_destroy_vm+0x2e8/0x470 arch/x86/kvm/x86.c:11676
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1217 [inline]
kvm_put_kvm+0x4fa/0xb00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1250
kvm_vm_release+0x3f/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1273
__fput+0x286/0x9f0 fs/file_table.c:311
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0xb29/0x2a30 kernel/exit.c:806
do_group_exit+0xd2/0x2f0 kernel/exit.c:935
get_signal+0x4b0/0x28c0 kernel/signal.c:2862
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK> |
| In the Linux kernel, the following vulnerability has been resolved:
USB: core: Fix hang in usb_kill_urb by adding memory barriers
The syzbot fuzzer has identified a bug in which processes hang waiting
for usb_kill_urb() to return. It turns out the issue is not unlinking
the URB; that works just fine. Rather, the problem arises when the
wakeup notification that the URB has completed is not received.
The reason is memory-access ordering on SMP systems. In outline form,
usb_kill_urb() and __usb_hcd_giveback_urb() operating concurrently on
different CPUs perform the following actions:
CPU 0 CPU 1
---------------------------- ---------------------------------
usb_kill_urb(): __usb_hcd_giveback_urb():
... ...
atomic_inc(&urb->reject); atomic_dec(&urb->use_count);
... ...
wait_event(usb_kill_urb_queue,
atomic_read(&urb->use_count) == 0);
if (atomic_read(&urb->reject))
wake_up(&usb_kill_urb_queue);
Confining your attention to urb->reject and urb->use_count, you can
see that the overall pattern of accesses on CPU 0 is:
write urb->reject, then read urb->use_count;
whereas the overall pattern of accesses on CPU 1 is:
write urb->use_count, then read urb->reject.
This pattern is referred to in memory-model circles as SB (for "Store
Buffering"), and it is well known that without suitable enforcement of
the desired order of accesses -- in the form of memory barriers -- it
is entirely possible for one or both CPUs to execute their reads ahead
of their writes. The end result will be that sometimes CPU 0 sees the
old un-decremented value of urb->use_count while CPU 1 sees the old
un-incremented value of urb->reject. Consequently CPU 0 ends up on
the wait queue and never gets woken up, leading to the observed hang
in usb_kill_urb().
The same pattern of accesses occurs in usb_poison_urb() and the
failure pathway of usb_hcd_submit_urb().
The problem is fixed by adding suitable memory barriers. To provide
proper memory-access ordering in the SB pattern, a full barrier is
required on both CPUs. The atomic_inc() and atomic_dec() accesses
themselves don't provide any memory ordering, but since they are
present, we can use the optimized smp_mb__after_atomic() memory
barrier in the various routines to obtain the desired effect.
This patch adds the necessary memory barriers. |
