From: Martin Pieuchot <[email protected]>
Date: Tue, 8 Nov 2022 11:12:43 +0000
> On 01/11/22(Tue) 15:26, Masato Asou wrote:
>> Hi,
>>
>> Return error number instead of call panic().
>
> Makes sense to me. Do you know how this error can occur? Is is a logic
> error or are we trusting values produced by a third party?
You can reproduce this error by writing 1025 bytes from Dom0 and
reading this from OpenBSD on the DomU as follows:
dom0$ sudo xenstore-write /vm/408d6e98-1b95-43c2-803b-de24ee205631/data
012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789abcde
domu$ hostctl /vm/408d6e98-1b95-43c2-803b-de24ee205631/data
--
ASOU Masato
>> comment, ok?
>> --
>> ASOU Masato
>>
>> diff --git a/sys/dev/pv/xenstore.c b/sys/dev/pv/xenstore.c
>> index 1e4f15d30eb..dc89ba0fa6d 100644
>> --- a/sys/dev/pv/xenstore.c
>> +++ b/sys/dev/pv/xenstore.c
>> @@ -118,6 +118,7 @@ struct xs_msg {
>> struct xs_msghdr xsm_hdr;
>> uint32_t xsm_read;
>> uint32_t xsm_dlen;
>> + int xsm_error;
>> uint8_t *xsm_data;
>> TAILQ_ENTRY(xs_msg) xsm_link;
>> };
>> @@ -566,9 +567,7 @@ xs_intr(void *arg)
>> }
>>
>> if (xsm->xsm_hdr.xmh_len > xsm->xsm_dlen)
>> - panic("message too large: %d vs %d for type %d, rid %u",
>> - xsm->xsm_hdr.xmh_len, xsm->xsm_dlen, xsm->xsm_hdr.xmh_type,
>> - xsm->xsm_hdr.xmh_rid);
>> + xsm->xsm_error = EMSGSIZE;
>>
>> len = MIN(xsm->xsm_hdr.xmh_len - xsm->xsm_read, avail);
>> if (len) {
>> @@ -800,7 +799,9 @@ xs_cmd(struct xs_transaction *xst, int cmd, const char
>> *path,
>> error = xs_geterror(xsm);
>> DPRINTF("%s: xenstore request %d \"%s\" error %s\n",
>> xs->xs_sc->sc_dev.dv_xname, cmd, path, xsm->xsm_data);
>> - } else if (mode == READ) {
>> + } else if (xsm->xsm_error != 0)
>> + error = xsm->xsm_error;
>> + else if (mode == READ) {
>> KASSERT(iov && iov_cnt);
>> error = xs_parse(xst, xsm, iov, iov_cnt);
>> }
>>
