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[Qemu-devel] [PATCH 2/3] m25p80: avoid out of bounds accesses
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 2/3] m25p80: avoid out of bounds accesses |
Date: |
Tue, 28 Jun 2016 10:39:29 +0200 |
s->cur_addr can be made to point outside s->storage, either by
writing a value >= 128 to s->ear (because s->ear * MAX_3BYTES_SIZE
is a signed integer and sign-extends into the 64-bit cur_addr),
or just by writing an address beyond the size of the flash being
emulated. Avoid the sign extension to make the code cleaner, and
on top of that mask s->cur_addr to s->size.
Signed-off-by: Paolo Bonzini <address@hidden>
---
hw/block/m25p80.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
index dd6714d..76a9bcf 100644
--- a/hw/block/m25p80.c
+++ b/hw/block/m25p80.c
@@ -586,18 +586,16 @@ static inline int get_addr_length(Flash *s)
static void complete_collecting_data(Flash *s)
{
- int i;
-
- s->cur_addr = 0;
+ int i, n;
- for (i = 0; i < get_addr_length(s); ++i) {
+ n = get_addr_length(s);
+ s->cur_addr = (n == 3 ? s->ear : 0);
+ for (i = 0; i < n; ++i) {
s->cur_addr <<= 8;
s->cur_addr |= s->data[i];
}
- if (get_addr_length(s) == 3) {
- s->cur_addr += s->ear * MAX_3BYTES_SIZE;
- }
+ s->cur_addr &= s->size - 1;
s->state = STATE_IDLE;
@@ -1099,14 +1097,14 @@ static uint32_t m25p80_transfer8(SSISlave *ss, uint32_t
tx)
DB_PRINT_L(1, "page program cur_addr=%#" PRIx64 " data=%" PRIx8 "\n",
s->cur_addr, (uint8_t)tx);
flash_write8(s, s->cur_addr, (uint8_t)tx);
- s->cur_addr++;
+ s->cur_addr = (s->cur_addr + 1) & (s->size - 1);
break;
case STATE_READ:
r = s->storage[s->cur_addr];
DB_PRINT_L(1, "READ 0x%" PRIx64 "=%" PRIx8 "\n", s->cur_addr,
(uint8_t)r);
- s->cur_addr = (s->cur_addr + 1) % s->size;
+ s->cur_addr = (s->cur_addr + 1) & (s->size - 1);
break;
case STATE_COLLECTING_DATA:
--
2.7.4