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authorThomas Huth <thuth@redhat.com>2023-05-22 11:10:11 +0200
committerMichael Tokarev <mjt@tls.msk.ru>2023-05-26 18:56:39 +0300
commite49884a90987744ddb54b2fadc770633eb6a4d62 (patch)
treeaa30e0b7dd99d2b400012a1b46676fd4279cf4b2 /hw/scsi
parent9d622451fdf9693a2265d5c04b041627f81d8c1d (diff)
hw/scsi/lsi53c895a: Fix reentrancy issues in the LSI controller (CVE-2023-0330)
We cannot use the generic reentrancy guard in the LSI code, so we have to manually prevent endless reentrancy here. The problematic lsi_execute_script() function has already a way to detect whether too many instructions have been executed - we just have to slightly change the logic here that it also takes into account if the function has been called too often in a reentrant way. The code in fuzz-lsi53c895a-test.c has been taken from an earlier patch by Mauro Matteo Cascella. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1563 Message-Id: <20230522091011.1082574-1-thuth@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Alexander Bulekov <alxndr@bu.edu> Signed-off-by: Thomas Huth <thuth@redhat.com> (cherry picked from commit b987718bbb1d0eabf95499b976212dd5f0120d75) Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Diffstat (limited to 'hw/scsi')
-rw-r--r--hw/scsi/lsi53c895a.c23
1 files changed, 17 insertions, 6 deletions
diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index af93557a9a..bbf32d3f73 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -1134,15 +1134,24 @@ static void lsi_execute_script(LSIState *s)
uint32_t addr, addr_high;
int opcode;
int insn_processed = 0;
+ static int reentrancy_level;
+
+ reentrancy_level++;
s->istat1 |= LSI_ISTAT1_SRUN;
again:
- if (++insn_processed > LSI_MAX_INSN) {
- /* Some windows drivers make the device spin waiting for a memory
- location to change. If we have been executed a lot of code then
- assume this is the case and force an unexpected device disconnect.
- This is apparently sufficient to beat the drivers into submission.
- */
+ /*
+ * Some windows drivers make the device spin waiting for a memory location
+ * to change. If we have executed more than LSI_MAX_INSN instructions then
+ * assume this is the case and force an unexpected device disconnect. This
+ * is apparently sufficient to beat the drivers into submission.
+ *
+ * Another issue (CVE-2023-0330) can occur if the script is programmed to
+ * trigger itself again and again. Avoid this problem by stopping after
+ * being called multiple times in a reentrant way (8 is an arbitrary value
+ * which should be enough for all valid use cases).
+ */
+ if (++insn_processed > LSI_MAX_INSN || reentrancy_level > 8) {
if (!(s->sien0 & LSI_SIST0_UDC)) {
qemu_log_mask(LOG_GUEST_ERROR,
"lsi_scsi: inf. loop with UDC masked");
@@ -1596,6 +1605,8 @@ again:
}
}
trace_lsi_execute_script_stop();
+
+ reentrancy_level--;
}
static uint8_t lsi_reg_readb(LSIState *s, int offset)