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authorFabiano Rosas <farosas@linux.ibm.com>2021-08-05 18:26:14 -0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-09-18 13:40:15 +0200
commitbda5602c1c35fb22847951607776d49352322e47 (patch)
tree9b7061bb8ddb61d34d38100886ebf1ff88227035 /arch
parent926bf91248dd12b5f93620a05f082c662b84db9d (diff)
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KVM: PPC: Book3S HV: Fix copy_tofrom_guest routines
[ Upstream commit 5d7d6dac8fe99ed59eee2300e4a03370f94d5222 ] 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 Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kvm/book3s_64_mmu_radix.c6
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 bb35490400e9..04028f905e50 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -64,10 +64,12 @@ 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)