diff options
| author | Fabiano Rosas <farosas@linux.ibm.com> | 2021-08-05 18:26:14 -0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-08-24 23:14:06 +1000 |
| commit | 5d7d6dac8fe99ed59eee2300e4a03370f94d5222 (patch) | |
| tree | 3c7e95f3721680ed9b70aa0b420dcfaa91a9ddd2 /arch/powerpc | |
| parent | e1ab9a730b426fadc018f91b7c98412473e542fb (diff) | |
KVM: PPC: Book3S HV: Fix copy_tofrom_guest routines
The __kvmhv_copy_tofrom_guest_radix function was introduced along with
nested HV guest support. It uses the platform's Radix MMU quadrants to
provide a nested hypervisor with fast access to its nested guests
memory (H_COPY_TOFROM_GUEST hypercall). It has also since been added
as a fast path for the kvmppc_ld/st routines which are used during
instruction emulation.
The commit def0bfdbd603 ("powerpc: use probe_user_read() and
probe_user_write()") changed the low level copy function from
raw_copy_from_user to probe_user_read, which adds a check to
access_ok. In powerpc that is:
static inline bool __access_ok(unsigned long addr, unsigned long size)
{
return addr < TASK_SIZE_MAX && size <= TASK_SIZE_MAX - addr;
}
and TASK_SIZE_MAX is 0x0010000000000000UL for 64-bit, which means that
setting the two MSBs of the effective address (which correspond to the
quadrant) now cause access_ok to reject the access.
This was not caught earlier because the most common code path via
kvmppc_ld/st contains a fallback (kvm_read_guest) that is likely to
succeed for L1 guests. For nested guests there is no fallback.
Another issue is that probe_user_read (now __copy_from_user_nofault)
does not return the number of bytes not copied in case of failure, so
the destination memory is not being cleared anymore in
kvmhv_copy_from_guest_radix:
ret = kvmhv_copy_tofrom_guest_radix(vcpu, eaddr, to, NULL, n);
if (ret > 0) <-- always false!
memset(to + (n - ret), 0, ret);
This patch fixes both issues by skipping access_ok and open-coding the
low level __copy_to/from_user_inatomic.
Fixes: def0bfdbd603 ("powerpc: use probe_user_read() and probe_user_write()")
Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210805212616.2641017-2-farosas@linux.ibm.com
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kvm/book3s_64_mmu_radix.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index b5905ae4377c..44eb7b1ef289 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -65,10 +65,12 @@ unsigned long __kvmhv_copy_tofrom_guest_radix(int lpid, int pid, } isync(); + pagefault_disable(); if (is_load) - ret = copy_from_user_nofault(to, (const void __user *)from, n); + ret = __copy_from_user_inatomic(to, (const void __user *)from, n); else - ret = copy_to_user_nofault((void __user *)to, from, n); + ret = __copy_to_user_inatomic((void __user *)to, from, n); + pagefault_enable(); /* switch the pid first to avoid running host with unallocated pid */ if (quadrant == 1 && pid != old_pid) |