linux-stable.git/arch/csky, branch linux-5.4.y

csky, hexagon: fix broken sys_sync_file_range

2024-07-05T07:08:31+00:00

commit 3339b99ef6fe38dac43b534cba3a8a0e29fb2eff upstream.

Both of these architectures require u64 function arguments to be
passed in even/odd pairs of registers or stack slots, which in case of
sync_file_range would result in a seven-argument system call that is
not currently possible. The system call is therefore incompatible with
all existing binaries.

While it would be possible to implement support for seven arguments
like on mips, it seems better to use a six-argument version, either
with the normal argument order but misaligned as on most architectures
or with the reordered sync_file_range2() calling conventions as on
arm and powerpc.

Cc: stable@vger.kernel.org
Acked-by: Guo Ren 
Signed-off-by: Arnd Bergmann 
Signed-off-by: Greg Kroah-Hartman

dma-mapping: drop the dev argument to arch_sync_dma_for_*

2023-04-05T09:16:43+00:00

[ Upstream commit 56e35f9c5b87ec1ae93e483284e189c84388de16 ]

These are pure cache maintainance routines, so drop the unused
struct device argument.

Signed-off-by: Christoph Hellwig 
Suggested-by: Daniel Vetter 
Stable-dep-of: ab327f8acdf8 ("mips: bmips: BCM6358: disable RAC flush for TP1")
Signed-off-by: Sasha Levin

csky: Fix function name in csky_alignment() and die()

2023-02-06T06:52:49+00:00

commit 751971af2e3615dc5bd12674080bc795505fefeb upstream.

When building ARCH=csky defconfig:

arch/csky/kernel/traps.c: In function 'die':
arch/csky/kernel/traps.c:112:17: error: implicit declaration of function
'make_dead_task' [-Werror=implicit-function-declaration]
  112 |                 make_dead_task(SIGSEGV);
      |                 ^~~~~~~~~~~~~~

The function's name is make_task_dead(), change it so there is no more
build error.

Fixes: 0e25498f8cd4 ("exit: Add and use make_task_dead.")
Signed-off-by: Nathan Chancellor 
Reviewed-by: Guo Ren 
Link: https://lkml.kernel.org/r/20211227184851.2297759-4-nathan@kernel.org
Signed-off-by: Eric W. Biederman 
Signed-off-by: Eric Biggers 
Signed-off-by: Sasha Levin

exit: Add and use make_task_dead.

2023-02-06T06:52:49+00:00

commit 0e25498f8cd43c1b5aa327f373dd094e9a006da7 upstream.

There are two big uses of do_exit.  The first is it's design use to be
the guts of the exit(2) system call.  The second use is to terminate
a task after something catastrophic has happened like a NULL pointer
in kernel code.

Add a function make_task_dead that is initialy exactly the same as
do_exit to cover the cases where do_exit is called to handle
catastrophic failure.  In time this can probably be reduced to just a
light wrapper around do_task_dead. For now keep it exactly the same so
that there will be no behavioral differences introducing this new
concept.

Replace all of the uses of do_exit that use it for catastraphic
task cleanup with make_task_dead to make it clear what the code
is doing.

As part of this rename rewind_stack_do_exit
rewind_stack_and_make_dead.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Eric Biggers 
Signed-off-by: Sasha Levin

perf: Protect perf_guest_cbs with RCU

2022-01-20T08:19:18+00:00

commit ff083a2d972f56bebfd82409ca62e5dfce950961 upstream.

Protect perf_guest_cbs with RCU to fix multiple possible errors.  Luckily,
all paths that read perf_guest_cbs already require RCU protection, e.g. to
protect the callback chains, so only the direct perf_guest_cbs touchpoints
need to be modified.

Bug #1 is a simple lack of WRITE_ONCE/READ_ONCE behavior to ensure
perf_guest_cbs isn't reloaded between a !NULL check and a dereference.
Fixed via the READ_ONCE() in rcu_dereference().

Bug #2 is that on weakly-ordered architectures, updates to the callbacks
themselves are not guaranteed to be visible before the pointer is made
visible to readers.  Fixed by the smp_store_release() in
rcu_assign_pointer() when the new pointer is non-NULL.

Bug #3 is that, because the callbacks are global, it's possible for
readers to run in parallel with an unregisters, and thus a module
implementing the callbacks can be unloaded while readers are in flight,
resulting in a use-after-free.  Fixed by a synchronize_rcu() call when
unregistering callbacks.

Bug #1 escaped notice because it's extremely unlikely a compiler will
reload perf_guest_cbs in this sequence.  perf_guest_cbs does get reloaded
for future derefs, e.g. for ->is_user_mode(), but the ->is_in_guest()
guard all but guarantees the consumer will win the race, e.g. to nullify
perf_guest_cbs, KVM has to completely exit the guest and teardown down
all VMs before KVM start its module unload / unregister sequence.  This
also makes it all but impossible to encounter bug #3.

Bug #2 has not been a problem because all architectures that register
callbacks are strongly ordered and/or have a static set of callbacks.

But with help, unloading kvm_intel can trigger bug #1 e.g. wrapping
perf_guest_cbs with READ_ONCE in perf_misc_flags() while spamming
kvm_intel module load/unload leads to:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: 0000 [#1] PREEMPT SMP
  CPU: 6 PID: 1825 Comm: stress Not tainted 5.14.0-rc2+ #459
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
  RIP: 0010:perf_misc_flags+0x1c/0x70
  Call Trace:
   perf_prepare_sample+0x53/0x6b0
   perf_event_output_forward+0x67/0x160
   __perf_event_overflow+0x52/0xf0
   handle_pmi_common+0x207/0x300
   intel_pmu_handle_irq+0xcf/0x410
   perf_event_nmi_handler+0x28/0x50
   nmi_handle+0xc7/0x260
   default_do_nmi+0x6b/0x170
   exc_nmi+0x103/0x130
   asm_exc_nmi+0x76/0xbf

Fixes: 39447b386c84 ("perf: Enhance perf to allow for guest statistic collection from host")
Signed-off-by: Sean Christopherson 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Paolo Bonzini 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211111020738.2512932-2-seanjc@google.com
Signed-off-by: Greg Kroah-Hartman

csky: Fixup regs.sr broken in ptrace

2021-10-20T09:40:12+00:00

commit af89ebaa64de726ca0a39bbb0bf0c81a1f43ad50 upstream.

gpr_get() return the entire pt_regs (include sr) to userspace, if we
don't restore the C bit in gpr_set, it may break the ALU result in
that context. So the C flag bit is part of gpr context, that's why
riscv totally remove the C bit in the ISA. That makes sr reg clear
from userspace to supervisor privilege.

Signed-off-by: Guo Ren 
Cc: Al Viro 
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

csky: don't let sigreturn play with priveleged bits of status register

2021-10-20T09:40:12+00:00

commit fbd63c08cdcca5fb1315aca3172b3c9c272cfb4f upstream.

csky restore_sigcontext() blindly overwrites regs->sr with the value
it finds in sigcontext.  Attacker can store whatever they want in there,
which includes things like S-bit.  Userland shouldn't be able to set
that, or anything other than C flag (bit 0).

Do the same thing other architectures with protected bits in flags
register do - preserve everything that shouldn't be settable in
user mode, picking the rest from the value saved is sigcontext.

Signed-off-by: Al Viro 
Signed-off-by: Guo Ren 
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

csky: change a Kconfig symbol name to fix e1000 build error

2021-04-28T11:19:16+00:00

[ Upstream commit d199161653d612b8fb96ac51bfd5b2d2782ecef3 ]

e1000's #define of CONFIG_RAM_BASE conflicts with a Kconfig symbol in
arch/csky/Kconfig.

The symbol in e1000 has been around longer, so change arch/csky/ to use
DRAM_BASE instead of RAM_BASE to remove the conflict.  (although e1000
is also a 2-line change)

Link: https://lkml.kernel.org/r/20210411055335.7111-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap 
Reported-by: kernel test robot 
Acked-by: Guo Ren 
Cc: Jesse Brandeburg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

csky: Fixup abiv2 syscall_trace break a4 & a5

2020-06-17T14:40:21+00:00

[ Upstream commit e0bbb53843b5fdfe464b099217e3b9d97e8a75d7 ]

Current implementation could destory a4 & a5 when strace, so we need to get them
from pt_regs by SAVE_ALL.

Signed-off-by: Guo Ren 
Signed-off-by: Sasha Levin

csky: Fixup raw_copy_from_user()

2020-06-03T06:21:15+00:00

[ Upstream commit 51bb38cb78363fdad1f89e87357b7bc73e39ba88 ]

If raw_copy_from_user(to, from, N) returns K, callers expect
the first N - K bytes starting at to to have been replaced with
the contents of corresponding area starting at from and the last
K bytes of destination *left* *unmodified*.

What arch/sky/lib/usercopy.c is doing is broken - it can lead to e.g.
data corruption on write(2).

raw_copy_to_user() is inaccurate about return value, which is a bug,
but consequences are less drastic than for raw_copy_from_user().
And just what are those access_ok() doing in there?  I mean, look into
linux/uaccess.h; that's where we do that check (as well as zero tail
on failure in the callers that need zeroing).

AFAICS, all of that shouldn't be hard to fix; something like a patch
below might make a useful starting point.

I would suggest moving these macros into usercopy.c (they are never
used anywhere else) and possibly expanding them there; if you leave
them alive, please at least rename __copy_user_zeroing(). Again,
it must not zero anything on failed read.

Said that, I'm not sure we won't be better off simply turning
usercopy.c into usercopy.S - all that is left there is a couple of
functions, each consisting only of inline asm.

Guo Ren reply:

Yes, raw_copy_from_user is wrong, it's no need zeroing code.

unsigned long _copy_from_user(void *to, const void __user *from,
unsigned long n)
{
        unsigned long res = n;
        might_fault();
        if (likely(access_ok(from, n))) {
                kasan_check_write(to, n);
                res = raw_copy_from_user(to, from, n);
        }
        if (unlikely(res))
                memset(to + (n - res), 0, res);
        return res;
}
EXPORT_SYMBOL(_copy_from_user);

You are right and access_ok() should be removed.

but, how about:
do {
...
        "2:     stw     %3, (%1, 0)     \n"             \
+       "       subi    %0, 4          \n"               \
        "9:     stw     %4, (%1, 4)     \n"             \
+       "       subi    %0, 4          \n"               \
        "10:    stw     %5, (%1, 8)     \n"             \
+       "       subi    %0, 4          \n"               \
        "11:    stw     %6, (%1, 12)    \n"             \
+       "       subi    %0, 4          \n"               \
        "       addi    %2, 16          \n"             \
        "       addi    %1, 16          \n"             \

Don't expand __ex_table

AI Viro reply:

Hey, I've no idea about the instruction scheduling on csky -
if that doesn't slow the things down, all the better.  It's just
that copy_to_user() and friends are on fairly hot codepaths,
and in quite a few situations they will dominate the speed of
e.g. read(2).  So I tried to keep the fast path unchanged.
Up to the architecture maintainers, obviously.  Which would be
you...

As for the fixups size increase (__ex_table size is unchanged)...
You have each of those macros expanded exactly once.
So the size is not a serious argument, IMO - useless complexity
would be, if it is, in fact, useless; the size... not really,
especially since those extra subi will at least offset it.

Again, up to you - asm optimizations of (essentially)
memcpy()-style loops are tricky and can depend upon the
fairly subtle details of architecture.  So even on something
I know reasonably well I would resort to direct experiments
if I can't pass the buck to architecture maintainers.

It *is* worth optimizing - this is where read() from a file
that is already in page cache spends most of the time, etc.

Guo Ren reply:

Thx, after fixup some typo “sub %0, 4”, apply the patch.

TODO:
 - user copy/from codes are still need optimizing.

Signed-off-by: Al Viro 
Signed-off-by: Guo Ren 
Signed-off-by: Sasha Levin