[PATCH] scsi: check inquiry buffer length to prevent crash

[Théo Maillart]

Using linux 6.x guest, at boot time, an inquiry makes qemu crash.
Here is a trace of the scsi inquiry in question:

scsi_req_parsed target 1 lun 0 tag 0x2cffb48 command 18 dir 1 length 4
scsi_req_parsed_lba target 1 lun 0 tag 0x2cffb48 command 18 lba 110592
scsi_req_alloc target 1 lun 0 tag 0x2cffb48
scsi_inquiry target 1 lun 0 tag 0x2cffb48 page 0x01/0xb0
scsi_generic_send_command Command: data= 0x12 0x01 0xb0 0x00 0x04 0x00
scsi_req_continue target 1 lun 0 tag 0x2cffb48
scsi_generic_read_data scsi_read_data tag=0x2cffb48
scsi_generic_aio_sgio_command generic aio sgio: tag=0x2cffb48 cmd=0x12 
timeout=30000
scsi_generic_read_complete Data ready tag=0x2cffb48 len=4
scsi_req_data target 1 lun 0 tag 0x2cffb48 len 4
scsi_req_continue target 1 lun 0 tag 0x2cffb48
scsi_generic_read_data scsi_read_data tag=0x2cffb48
scsi_generic_command_complete_noio Command complete 0x7fb0870b80 tag=0x2cffb48 
status=0
scsi_req_dequeue target 1 lun 0 tag 0x2cffb48

And here is a backtrace from the crash:

 #0  0x0000007face68580 in a_crash () at ./src/internal/atomic.h:250
 #1  get_nominal_size (end=0x7f6758f92c "", p=0x7f6758f920 "") at 
src/malloc/mallocng/meta.h:168
 #2  __libc_free (p=0x7f6758f920) at src/malloc/mallocng/free.c:110
 #3  0x0000005592f93ed8 in scsi_free_request (req=0x7fac2c6b50) at 
../hw/scsi/scsi-generic.c:70
 #4  0x0000005592f869b8 in scsi_req_unref (req=0x7fac2c6b50) at 
../hw/scsi/scsi-bus.c:1382
 #5  0x0000005592f94b7c in scsi_read_complete (opaque=0x7fac2c6b50, ret=0) at 
../hw/scsi/scsi-generic.c:354
 #6  0x0000005593659b90 in blk_aio_complete (acb=0x7f66c206a0) at 
../block/block-backend.c:1527
 #7  0x000000559365a3c8 in blk_aio_ioctl_entry (opaque=0x7f66c206a0) at 
../block/block-backend.c:1735
 #8  0x00000055937dee64 in coroutine_bootstrap (self=0x7f672f77e0, 
co=0x7f672f77e0) at ../util/coroutine-sigaltstack.c:104
 #9  0x00000055937deed8 in coroutine_trampoline (signal=12) at 
../util/coroutine-sigaltstack.c:145
 #10 <signal handler called>
 #11 __cp_end () at src/thread/aarch64/syscall_cp.s:30
 #12 0x0000007facea8214 in __syscall_cp_c (nr=133, u=<optimized out>, 
v=<optimized out>, w=<optimized out>, x=<optimized out>,
     y=<optimized out>, z=<optimized out>) at src/thread/pthread_cancel.c:33
 #13 0x0000007facefa020 in ?? ()

Signed-off-by: Théo Maillart <tmaillart@freebox.fr>
---
 hw/scsi/scsi-generic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index ac9fa662b4..25246589b7 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -191,7 +191,7 @@ static int scsi_handle_inquiry_reply(SCSIGenericReq *r, 
SCSIDevice *s, int len)
     if ((s->type == TYPE_DISK || s->type == TYPE_ZBC) &&
         (r->req.cmd.buf[1] & 0x01)) {
         page = r->req.cmd.buf[2];
-        if (page == 0xb0) {
+        if (page == 0xb0 && r->buflen >= 12) {
             uint64_t max_transfer = calculate_max_transfer(s);
             stl_be_p(&r->buf[8], max_transfer);
             /* Also take care of the opt xfer len. */
-- 
2.40.0