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hw/scsi/lsi53c895a: Fix reentrancy issues in the LSI controller (CVE-2023-0330)

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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>
This commit is contained in:
Thomas Huth 2023-05-22 11:10:11 +02:00
parent d139fe9ad8
commit b987718bbb
2 changed files with 50 additions and 6 deletions
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21
hw/scsi/lsi53c895a.c
View File

@ -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)

33
tests/qtest/fuzz-lsi53c895a-test.c
View File

@ -8,6 +8,36 @@
#include "qemu/osdep.h"
#include "libqtest.h"
/*
* This used to trigger a DMA reentrancy issue
* leading to memory corruption bugs like stack
* overflow or use-after-free
* https://gitlab.com/qemu-project/qemu/-/issues/1563
*/
static void test_lsi_dma_reentrancy(void)
{
QTestState *s;
s = qtest_init("-M q35 -m 512M -nodefaults "
"-blockdev driver=null-co,node-name=null0 "
"-device lsi53c810 -device scsi-cd,drive=null0");
qtest_outl(s, 0xcf8, 0x80000804); /* PCI Command Register */
qtest_outw(s, 0xcfc, 0x7); /* Enables accesses */
qtest_outl(s, 0xcf8, 0x80000814); /* Memory Bar 1 */
qtest_outl(s, 0xcfc, 0xff100000); /* Set MMIO Address*/
qtest_outl(s, 0xcf8, 0x80000818); /* Memory Bar 2 */
qtest_outl(s, 0xcfc, 0xff000000); /* Set RAM Address*/
qtest_writel(s, 0xff000000, 0xc0000024);
qtest_writel(s, 0xff000114, 0x00000080);
qtest_writel(s, 0xff00012c, 0xff000000);
qtest_writel(s, 0xff000004, 0xff000114);
qtest_writel(s, 0xff000008, 0xff100014);
qtest_writel(s, 0xff10002f, 0x000000ff);
qtest_quit(s);
}
/*
* This used to trigger a UAF in lsi_do_msgout()
* https://gitlab.com/qemu-project/qemu/-/issues/972
@ -124,5 +154,8 @@ int main(int argc, char **argv)
qtest_add_func("fuzz/lsi53c895a/lsi_do_msgout_cancel_req",
test_lsi_do_msgout_cancel_req);
qtest_add_func("fuzz/lsi53c895a/lsi_dma_reentrancy",
test_lsi_dma_reentrancy);
return g_test_run();
}