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[PULL,02/62] softmmu: Use memmove in flatview_write_continue

Message ID 20230301025643.1227244-3-richard.henderson@linaro.org
State Accepted
Commit 4a73aee88140fe7e4930375d3c786b10b2b5d447
Headers show
Series [PULL,01/62] exec/helper-head: Include missing "fpu/softfloat-types.h" header | expand

Commit Message

Richard Henderson March 1, 2023, 2:55 a.m. UTC 
From: Akihiko Odaki <akihiko.odaki@daynix.com>

We found a case where the source passed to flatview_write_continue() may
overlap with the destination when fuzzing igb, a new proposed network
device with sanitizers.

igb uses pci_dma_map() to get Tx packet, and pci_dma_write() to write Rx
buffer. While pci_dma_write() is usually used to write data from
memory not mapped to the guest, if igb is configured to perform
loopback, the data will be sourced from the guest memory. The source and
destination can overlap and the usage of memcpy() will be invalid in
such a case.

While we do not really have to deal with such an invalid request for
igb, detecting the overlap in igb code beforehand requires complex code,
and only covers this specific case. Instead, just replace memcpy() with
memmove() to tolerate overlaps. Using memmove() will slightly damage the
performance as it will need to check overlaps before using SIMD
instructions for copying, but the cost should be negligible, considering
the inherent complexity of flatview_write_continue().

The test cases generated by the fuzzer is available at:
https://patchew.org/QEMU/20230129053316.1071513-1-alxndr@bu.edu/

The fixed test case is:
fuzz/crash_47dfe62d9f911bf523ff48cd441b61c0013ed805

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Acked-by: Alexander Bulekov <alxndr@bu.edu>
Acked-by: David Hildenbrand <david@redhat.com>
Message-Id: <20230131030155.18932-1-akihiko.odaki@daynix.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 softmmu/physmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index df54b917a9..47143edb4f 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2637,7 +2637,7 @@  static MemTxResult flatview_write_continue(FlatView *fv, hwaddr addr,
         } else {
             /* RAM case */
             ram_ptr = qemu_ram_ptr_length(mr->ram_block, addr1, &l, false);
-            memcpy(ram_ptr, buf, l);
+            memmove(ram_ptr, buf, l);
             invalidate_and_set_dirty(mr, addr1, l);
         }