File 0248-softmmu-Always-initialize-xlat-in-a.patch of Package qemu.28156
From: Richard Henderson <richard.henderson@linaro.org>
Date: Tue, 21 Jun 2022 08:38:29 -0700
Subject: softmmu: Always initialize xlat in address_space_translate_for_iotlb
Git-commit: 418ade7849ce7641c0f7333718caf5091a02fd4c
References: bsc#1201367, CVE-2022-35414
The bug is an uninitialized memory read, along the translate_fail
path, which results in garbage being read from iotlb_to_section,
which can lead to a crash in io_readx/io_writex.
The bug may be fixed by writing any value with zero
in ~TARGET_PAGE_MASK, so that the call to iotlb_to_section using
the xlat'ed address returns io_mem_unassigned, as desired by the
translate_fail path.
It is most useful to record the original physical page address,
which will eventually be logged by memory_region_access_valid
when the access is rejected by unassigned_mem_accepts.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1065
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220621153829.366423-1-richard.henderson@linaro.org>
Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
---
exec.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/exec.c b/exec.c
index 9fa5aa871ea13048b395b7269b54..062a8882ea48fef2d44f7a26b09a 100644
--- a/exec.c
+++ b/exec.c
@@ -714,7 +714,7 @@ static void tcg_iommu_free_notifier_list(CPUState *cpu)
/* Called from RCU critical section */
MemoryRegionSection *
-address_space_translate_for_iotlb(CPUState *cpu, int asidx, hwaddr addr,
+address_space_translate_for_iotlb(CPUState *cpu, int asidx, hwaddr orig_addr,
hwaddr *xlat, hwaddr *plen,
MemTxAttrs attrs, int *prot)
{
@@ -723,6 +723,7 @@ address_space_translate_for_iotlb(CPUState *cpu, int asidx, hwaddr addr,
IOMMUMemoryRegionClass *imrc;
IOMMUTLBEntry iotlb;
int iommu_idx;
+ hwaddr addr = orig_addr;
AddressSpaceDispatch *d = atomic_rcu_read(&cpu->cpu_ases[asidx].memory_dispatch);
for (;;) {
@@ -766,6 +767,16 @@ address_space_translate_for_iotlb(CPUState *cpu, int asidx, hwaddr addr,
return section;
translate_fail:
+ /*
+ * We should be given a page-aligned address -- certainly
+ * tlb_set_page_with_attrs() does so. The page offset of xlat
+ * is used to index sections[], and PHYS_SECTION_UNASSIGNED = 0.
+ * The page portion of xlat will be logged by memory_region_access_valid()
+ * when this memory access is rejected, so use the original untranslated
+ * physical address.
+ */
+ assert((orig_addr & ~TARGET_PAGE_MASK) == 0);
+ *xlat = orig_addr;
return &d->map.sections[PHYS_SECTION_UNASSIGNED];
}
#endif