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reentrancy without mutexe #94

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reentrancy without mutexe #94

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Reneg973
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...sages are shorter than SPI_BUFSIZE

With the patch it is now possible to have multiple threads querying SPI devices in parallel without blocking. Includes pointer checks of tx and rx parameters.

Additional question:
A comment says /* portable code must never pass more than 32 bytes */!
So should max be replaced with min for SPI_BUFSIZ?

@Reneg973
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I've overseen that 'buf' must be DMA-safe, so there was also an issue within spi_init(), as it didn't set the flag GFP_DMA within kmalloc.

So patch needs additional modifications.

@Reneg973 Reneg973 closed this Mar 30, 2015
mihailescu2m pushed a commit to mihailescu2m/linux that referenced this pull request Dec 14, 2019
@gregkh
KVM: x86: Grab KVM's srcu lock when setting nested state
d61ce96 
commit ad5996d upstream.

Acquire kvm->srcu for the duration of ->set_nested_state() to fix a bug
where nVMX derefences ->memslots without holding ->srcu or ->slots_lock.

The other half of nested migration, ->get_nested_state(), does not need
to acquire ->srcu as it is a purely a dump of internal KVM (and CPU)
state to userspace.

Detected as an RCU lockdep splat that is 100% reproducible by running
KVM's state_test selftest with CONFIG_PROVE_LOCKING=y.  Note that the
failing function, kvm_is_visible_gfn(), is only checking the validity of
a gfn, it's not actually accessing guest memory (which is more or less
unsupported during vmx_set_nested_state() due to incorrect MMU state),
i.e. vmx_set_nested_state() itself isn't fundamentally broken.  In any
case, setting nested state isn't a fast path so there's no reason to go
out of our way to avoid taking ->srcu.

  =============================
  WARNING: suspicious RCU usage
  5.4.0-rc7+ hardkernel#94 Not tainted
  -----------------------------
  include/linux/kvm_host.h:626 suspicious rcu_dereference_check() usage!

               other info that might help us debug this:

  rcu_scheduler_active = 2, debug_locks = 1
  1 lock held by evmcs_test/10939:
   #0: ffff88826ffcb800 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0x85/0x630 [kvm]

  stack backtrace:
  CPU: 1 PID: 10939 Comm: evmcs_test Not tainted 5.4.0-rc7+ hardkernel#94
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
  Call Trace:
   dump_stack+0x68/0x9b
   kvm_is_visible_gfn+0x179/0x180 [kvm]
   mmu_check_root+0x11/0x30 [kvm]
   fast_cr3_switch+0x40/0x120 [kvm]
   kvm_mmu_new_cr3+0x34/0x60 [kvm]
   nested_vmx_load_cr3+0xbd/0x1f0 [kvm_intel]
   nested_vmx_enter_non_root_mode+0xab8/0x1d60 [kvm_intel]
   vmx_set_nested_state+0x256/0x340 [kvm_intel]
   kvm_arch_vcpu_ioctl+0x491/0x11a0 [kvm]
   kvm_vcpu_ioctl+0xde/0x630 [kvm]
   do_vfs_ioctl+0xa2/0x6c0
   ksys_ioctl+0x66/0x70
   __x64_sys_ioctl+0x16/0x20
   do_syscall_64+0x54/0x200
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7f59a2b95f47

Fixes: 8fcc4b5 ("kvm: nVMX: Introduce KVM_CAP_NESTED_STATE")
Cc: [email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
mdrjr pushed a commit that referenced this pull request May 11, 2021
@lzto @gregkh
net: wan/lmc: unregister device when no matching device is found
aca623d 
[ Upstream commit 62e69bc ]

lmc set sc->lmc_media pointer when there is a matching device.
However, when no matching device is found, this pointer is NULL
and the following dereference will result in a null-ptr-deref.

To fix this issue, unregister the hdlc device and return an error.

[    4.569359] BUG: KASAN: null-ptr-deref in lmc_init_one.cold+0x2b6/0x55d [lmc]
[    4.569748] Read of size 8 at addr 0000000000000008 by task modprobe/95
[    4.570102]
[    4.570187] CPU: 0 PID: 95 Comm: modprobe Not tainted 5.11.0-rc7 #94
[    4.570527] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-48-gd9c812dda519-preb4
[    4.571125] Call Trace:
[    4.571261]  dump_stack+0x7d/0xa3
[    4.571445]  kasan_report.cold+0x10c/0x10e
[    4.571667]  ? lmc_init_one.cold+0x2b6/0x55d [lmc]
[    4.571932]  lmc_init_one.cold+0x2b6/0x55d [lmc]
[    4.572186]  ? lmc_mii_readreg+0xa0/0xa0 [lmc]
[    4.572432]  local_pci_probe+0x6f/0xb0
[    4.572639]  pci_device_probe+0x171/0x240
[    4.572857]  ? pci_device_remove+0xe0/0xe0
[    4.573080]  ? kernfs_create_link+0xb6/0x110
[    4.573315]  ? sysfs_do_create_link_sd.isra.0+0x76/0xe0
[    4.573598]  really_probe+0x161/0x420
[    4.573799]  driver_probe_device+0x6d/0xd0
[    4.574022]  device_driver_attach+0x82/0x90
[    4.574249]  ? device_driver_attach+0x90/0x90
[    4.574485]  __driver_attach+0x60/0x100
[    4.574694]  ? device_driver_attach+0x90/0x90
[    4.574931]  bus_for_each_dev+0xe1/0x140
[    4.575146]  ? subsys_dev_iter_exit+0x10/0x10
[    4.575387]  ? klist_node_init+0x61/0x80
[    4.575602]  bus_add_driver+0x254/0x2a0
[    4.575812]  driver_register+0xd3/0x150
[    4.576021]  ? 0xffffffffc0018000
[    4.576202]  do_one_initcall+0x84/0x250
[    4.576411]  ? trace_event_raw_event_initcall_finish+0x150/0x150
[    4.576733]  ? unpoison_range+0xf/0x30
[    4.576938]  ? ____kasan_kmalloc.constprop.0+0x84/0xa0
[    4.577219]  ? unpoison_range+0xf/0x30
[    4.577423]  ? unpoison_range+0xf/0x30
[    4.577628]  do_init_module+0xf8/0x350
[    4.577833]  load_module+0x3fe6/0x4340
[    4.578038]  ? vm_unmap_ram+0x1d0/0x1d0
[    4.578247]  ? ____kasan_kmalloc.constprop.0+0x84/0xa0
[    4.578526]  ? module_frob_arch_sections+0x20/0x20
[    4.578787]  ? __do_sys_finit_module+0x108/0x170
[    4.579037]  __do_sys_finit_module+0x108/0x170
[    4.579278]  ? __ia32_sys_init_module+0x40/0x40
[    4.579523]  ? file_open_root+0x200/0x200
[    4.579742]  ? do_sys_open+0x85/0xe0
[    4.579938]  ? filp_open+0x50/0x50
[    4.580125]  ? exit_to_user_mode_prepare+0xfc/0x130
[    4.580390]  do_syscall_64+0x33/0x40
[    4.580586]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[    4.580859] RIP: 0033:0x7f1a724c3cf7
[    4.581054] Code: 48 89 57 30 48 8b 04 24 48 89 47 38 e9 1d a0 02 00 48 89 f8 48 89 f7 48 89 d6 48 891
[    4.582043] RSP: 002b:00007fff44941c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[    4.582447] RAX: ffffffffffffffda RBX: 00000000012ada70 RCX: 00007f1a724c3cf7
[    4.582827] RDX: 0000000000000000 RSI: 00000000012ac9e0 RDI: 0000000000000003
[    4.583207] RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000001
[    4.583587] R10: 00007f1a72527300 R11: 0000000000000246 R12: 00000000012ac9e0
[    4.583968] R13: 0000000000000000 R14: 00000000012acc90 R15: 0000000000000001
[    4.584349] ==================================================================

Signed-off-by: Tong Zhang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
mdrjr pushed a commit that referenced this pull request Sep 10, 2024
@YuKuai-huawei @gregkh
md/raid5: avoid BUG_ON() while continue reshape after reassembling
775a9ba 
[ Upstream commit 305a517 ]

Currently, mdadm support --revert-reshape to abort the reshape while
reassembling, as the test 07revert-grow. However, following BUG_ON()
can be triggerred by the test:

kernel BUG at drivers/md/raid5.c:6278!
invalid opcode: 0000 [#1] PREEMPT SMP PTI
irq event stamp: 158985
CPU: 6 PID: 891 Comm: md0_reshape Not tainted 6.9.0-03335-g7592a0b0049a #94
RIP: 0010:reshape_request+0x3f1/0xe60
Call Trace:
 <TASK>
 raid5_sync_request+0x43d/0x550
 md_do_sync+0xb7a/0x2110
 md_thread+0x294/0x2b0
 kthread+0x147/0x1c0
 ret_from_fork+0x59/0x70
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Root cause is that --revert-reshape update the raid_disks from 5 to 4,
while reshape position is still set, and after reassembling the array,
reshape position will be read from super block, then during reshape the
checking of 'writepos' that is caculated by old reshape position will
fail.

Fix this panic the easy way first, by converting the BUG_ON() to
WARN_ON(), and stop the reshape if checkings fail.

Noted that mdadm must fix --revert-shape as well, and probably md/raid
should enhance metadata validation as well, however this means
reassemble will fail and there must be user tools to fix the wrong
metadata.

Signed-off-by: Yu Kuai <[email protected]>
Signed-off-by: Song Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
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@Reneg973