linux-stable.git/arch/arm64/kernel/traps.c, branch linux-4.9.y

arm64: capabilities: Update prototype for enable call back

2022-04-12T05:52:14+00:00

[ Upstream commit c0cda3b8ee6b4b6851b2fd8b6db91fd7b0e2524a ]

We issue the enable() call back for all CPU hwcaps capabilities
available on the system, on all the CPUs. So far we have ignored
the argument passed to the call back, which had a prototype to
accept a "void *" for use with on_each_cpu() and later with
stop_machine(). However, with commit 0a0d111d40fd1
("arm64: cpufeature: Pass capability structure to ->enable callback"),
there are some users of the argument who wants the matching capability
struct pointer where there are multiple matching criteria for a single
capability. Clean up the declaration of the call back to make it clear.

 1) Renamed to cpu_enable(), to imply taking necessary actions on the
    called CPU for the entry.
 2) Pass const pointer to the capability, to allow the call back to
    check the entry. (e.,g to check if any action is needed on the CPU)
 3) We don't care about the result of the call back, turning this to
    a void.

Cc: Will Deacon 
Cc: Catalin Marinas 
Cc: Mark Rutland 
Cc: Andre Przywara 
Cc: James Morse 
Acked-by: Robin Murphy 
Reviewed-by: Julien Thierry 
Signed-off-by: Dave Martin 
[suzuki: convert more users, rename call back and drop results]
Signed-off-by: Suzuki K Poulose 
Signed-off-by: Will Deacon 
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: James Morse 
Signed-off-by: Greg Kroah-Hartman

arm64: Remove unimplemented syscall log message

2021-06-10T10:42:37+00:00

commit 1962682d2b2fbe6cfa995a85c53c069fadda473e upstream.

Stop printing a (ratelimited) kernel message for each instance of an
unimplemented syscall being called. Userland making an unimplemented
syscall is not necessarily misbehaviour and to be expected with a
current userland running on an older kernel. Also, the current message
looks scary to users but does not actually indicate a real problem nor
help them narrow down the cause. Just rely on sys_ni_syscall() to return
-ENOSYS.

Cc: 
Acked-by: Will Deacon 
Signed-off-by: Michael Weiser 
Signed-off-by: Will Deacon 
Signed-off-by: Arnd Bergmann 
Signed-off-by: Greg Kroah-Hartman

arm64: fix for bad_mode() handler to always result in panic

2019-11-28T17:29:02+00:00

commit e4ba15debcfd27f60d43da940a58108783bff2a6 upstream.

The bad_mode() handler is called if we encounter an uunknown exception,
with the expectation that the subsequent call to panic() will halt the
system. Unfortunately, if the exception calling bad_mode() is taken from
EL0, then the call to die() can end up killing the current user task and
calling schedule() instead of falling through to panic().

Remove the die() call altogether, since we really want to bring down the
machine in this "impossible" case.

Signed-off-by: Hari Vyas 
Signed-off-by: Will Deacon 
Signed-off-by: Catalin Marinas 
Signed-off-by: Lee Jones 
Signed-off-by: Greg Kroah-Hartman

arm64: traps: disable irq in die()

2019-03-27T05:13:04+00:00

commit 6f44a0bacb79a03972c83759711832b382b1b8ac upstream.

In current die(), the irq is disabled for __die() handle, not
including the possible panic() handling. Since the log in __die()
can take several hundreds ms, new irq might come and interrupt
current die().

If the process calling die() holds some critical resource, and some
other process scheduled later also needs it, then it would deadlock.
The first panic will not be executed.

So here disable irq for the whole flow of die().

Signed-off-by: Qiao Zhou 
Signed-off-by: Will Deacon 
Signed-off-by: Arnd Bergmann 
Signed-off-by: Greg Kroah-Hartman

arm64: Disable unhandled signal log messages by default

2018-02-28T09:18:31+00:00

commit 5ee39a71fd89ab7240c5339d04161c44a8e03269 upstream.

aarch64 unhandled signal kernel messages are very verbose, suggesting
them to be more of a debugging aid:

sigsegv[33]: unhandled level 2 translation fault (11) at 0x00000000, esr
0x92000046, in sigsegv[400000+71000]
CPU: 1 PID: 33 Comm: sigsegv Tainted: G        W        4.15.0-rc3+ #3
Hardware name: linux,dummy-virt (DT)
pstate: 60000000 (nZCv daif -PAN -UAO)
pc : 0x4003f4
lr : 0x4006bc
sp : 0000fffffe94a060
x29: 0000fffffe94a070 x28: 0000000000000000
x27: 0000000000000000 x26: 0000000000000000
x25: 0000000000000000 x24: 00000000004001b0
x23: 0000000000486ac8 x22: 00000000004001c8
x21: 0000000000000000 x20: 0000000000400be8
x19: 0000000000400b30 x18: 0000000000484728
x17: 000000000865ffc8 x16: 000000000000270f
x15: 00000000000000b0 x14: 0000000000000002
x13: 0000000000000001 x12: 0000000000000000
x11: 0000000000000000 x10: 0008000020008008
x9 : 000000000000000f x8 : ffffffffffffffff
x7 : 0004000000000000 x6 : ffffffffffffffff
x5 : 0000000000000000 x4 : 0000000000000000
x3 : 00000000004003e4 x2 : 0000fffffe94a1e8
x1 : 000000000000000a x0 : 0000000000000000

Disable them by default, so they can be enabled using
/proc/sys/debug/exception-trace.

Cc: 
Signed-off-by: Michael Weiser 
Signed-off-by: Will Deacon 
Signed-off-by: Greg Kroah-Hartman

arm64: ensure __dump_instr() checks addr_limit

2017-11-08T09:08:32+00:00

commit 7a7003b1da010d2b0d1dc8bf21c10f5c73b389f1 upstream.

It's possible for a user to deliberately trigger __dump_instr with a
chosen kernel address.

Let's avoid problems resulting from this by using get_user() rather than
__get_user(), ensuring that we don't erroneously access kernel memory.

Where we use __dump_instr() on kernel text, we already switch to
KERNEL_DS, so this shouldn't adversely affect those cases.

Fixes: 60ffc30d5652810d ("arm64: Exception handling")
Acked-by: Will Deacon 
Signed-off-by: Mark Rutland 
Signed-off-by: Catalin Marinas 
Signed-off-by: Greg Kroah-Hartman

arm64: traps: fix userspace cache maintenance emulation on a tagged pointer

2017-06-14T13:06:04+00:00

commit 81cddd65b5c82758ea5571a25e31ff6f1f89ff02 upstream.

This backport has a minor difference from the upstream commit, as v4.9
did not yet have the refactoring done by commit 8b6e70fccff2 ("arm64:
traps: correctly handle MRS/MSR with XZR").

Original patch description:

When we emulate userspace cache maintenance in the kernel, we can
currently send the task a SIGSEGV even though the maintenance was done
on a valid address. This happens if the address has a non-zero address
tag, and happens to not be mapped in.

When we get the address from a user register, we don't currently remove
the address tag before performing cache maintenance on it. If the
maintenance faults, we end up in either __do_page_fault, where find_vma
can't find the VMA if the address has a tag, or in do_translation_fault,
where the tagged address will appear to be above TASK_SIZE. In both
cases, the address is not mapped in, and the task is sent a SIGSEGV.

This patch removes the tag from the address before using it. With this
patch, the fault is handled correctly, the address gets mapped in, and
the cache maintenance succeeds.

As a second bug, if cache maintenance (correctly) fails on an invalid
tagged address, the address gets passed into arm64_notify_segfault,
where find_vma fails to find the VMA due to the tag, and the wrong
si_code may be sent as part of the siginfo_t of the segfault. With this
patch, the correct si_code is sent.

Fixes: 7dd01aef0557 ("arm64: trap userspace "dc cvau" cache operation on errata-affected core")
Acked-by: Will Deacon
Signed-off-by: Kristina Martsenko
Signed-off-by: Catalin Marinas
Signed-off-by: Greg Kroah-Hartman

arm64: avoid returning from bad_mode

2017-01-26T07:24:40+00:00

commit 7d9e8f71b989230bc613d121ca38507d34ada849 upstream.

Generally, taking an unexpected exception should be a fatal event, and
bad_mode is intended to cater for this. However, it should be possible
to contain unexpected synchronous exceptions from EL0 without bringing
the kernel down, by sending a SIGILL to the task.

We tried to apply this approach in commit 9955ac47f4ba1c95 ("arm64:
don't kill the kernel on a bad esr from el0"), by sending a signal for
any bad_mode call resulting from an EL0 exception.

However, this also applies to other unexpected exceptions, such as
SError and FIQ. The entry paths for these exceptions branch to bad_mode
without configuring the link register, and have no kernel_exit. Thus, if
we take one of these exceptions from EL0, bad_mode will eventually
return to the original user link register value.

This patch fixes this by introducing a new bad_el0_sync handler to cater
for the recoverable case, and restoring bad_mode to its original state,
whereby it calls panic() and never returns. The recoverable case
branches to bad_el0_sync with a bl, and returns to userspace via the
usual ret_to_user mechanism.

Signed-off-by: Mark Rutland 
Fixes: 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0")
Reported-by: Mark Salter 
Cc: Will Deacon 
Signed-off-by: Catalin Marinas 
Signed-off-by: Greg Kroah-Hartman

arm64: cpufeature: Schedule enable() calls instead of calling them via IPI

2016-10-20T08:50:53+00:00

The enable() call for a cpufeature/errata is called using on_each_cpu().
This issues a cross-call IPI to get the work done. Implicitly, this
stashes the running PSTATE in SPSR when the CPU receives the IPI, and
restores it when we return. This means an enable() call can never modify
PSTATE.

To allow PAN to do this, change the on_each_cpu() call to use
stop_machine(). This schedules the work on each CPU which allows
us to modify PSTATE.

This involves changing the protype of all the enable() functions.

enable_cpu_capabilities() is called during boot and enables the feature
on all online CPUs. This path now uses stop_machine(). CPU features for
hotplug'd CPUs are enabled by verify_local_cpu_features() which only
acts on the local CPU, and can already modify the running PSTATE as it
is called from secondary_start_kernel().

Reported-by: Tony Thompson 
Reported-by: Vladimir Murzin 
Signed-off-by: James Morse 
Cc: Suzuki K Poulose 
Signed-off-by: Will Deacon

arm64: Cortex-A53 errata workaround: check for kernel addresses

2016-10-20T08:50:49+00:00

Commit 7dd01aef0557 ("arm64: trap userspace "dc cvau" cache operation on
errata-affected core") adds code to execute cache maintenance instructions
in the kernel on behalf of userland on CPUs with certain ARM CPU errata.
It turns out that the address hasn't been checked to be a valid user
space address, allowing userland to clean cache lines in kernel space.
Fix this by introducing an address check before executing the
instructions on behalf of userland.

Since the address doesn't come via a syscall parameter, we can't just
reject tagged pointers and instead have to remove the tag when checking
against the user address limit.

Cc: 
Fixes: 7dd01aef0557 ("arm64: trap userspace "dc cvau" cache operation on errata-affected core")
Reported-by: Kristina Martsenko 
Signed-off-by: Andre Przywara 
[will: rework commit message + replace access_ok with max_user_addr()]
Signed-off-by: Will Deacon