On 5/17/22 22:52, Ilya Maximets wrote: > On 4/26/22 17:16, Dumitru Ceara wrote: >> On 4/26/22 16:29, Adrian Moreno wrote: >>> >>> >>> On 4/12/22 15:29, Dumitru Ceara wrote: >>>> When compiled with '-fsanitize=undefined' running 'ovsdb-client >>>> --timestamp monitor Open_vSwitch' in a sandbox triggers the following >>>> undefined behavior (flagged by UBSan): >>>> >>>> lib/dynamic-string.c:207:38: runtime error: applying zero offset to >>>> null pointer >>>> #0 0x196c05b in ds_put_strftime_msec lib/dynamic-string.c:207:38 >>>> #1 0x196c2aa in xastrftime_msec lib/dynamic-string.c:225:5 >>>> #2 0x1935f33 in pmd_info_show_perf lib/dpif-netdev.c:799:17 >>>> #3 0x1935f33 in dpif_netdev_pmd_info lib/dpif-netdev.c:1487:13 >>>> #4 0x1938155 in pmd_perf_show_cmd lib/dpif-netdev.c:1537:5 >>>> #5 0x1d7634b in process_command lib/unixctl.c:310:13 >>>> #6 0x1d7634b in run_connection lib/unixctl.c:344:17 >>>> #7 0x1d7634b in unixctl_server_run lib/unixctl.c:395:21 >>>> #8 0x168b5bd in main vswitchd/ovs-vswitchd.c:130:9 >>>> #9 0x7f6fa2fd8492 in __libc_start_main (/lib64/libc.so.6+0x23492) >>>> #10 0xe6911d in _start (vswitchd/ovs-vswitchd+0xe6911d) >>>> >>>> Reported-by: Ilya Maximets <[email protected]> >>>> Signed-off-by: Dumitru Ceara <[email protected]> >>>> --- >>>> lib/dynamic-string.c | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/lib/dynamic-string.c b/lib/dynamic-string.c >>>> index fd0127ed1740..3d415af4f4e0 100644 >>>> --- a/lib/dynamic-string.c >>>> +++ b/lib/dynamic-string.c >>>> @@ -200,8 +200,8 @@ ds_put_strftime_msec(struct ds *ds, const char >>>> *template, long long int when, >>>> for (;;) { >>>> size_t avail = ds->string ? ds->allocated - ds->length + 1 : 0; >>>> - size_t used = strftime_msec(&ds->string[ds->length], avail, >>>> template, >>>> - &tm); >>>> + char *dest = ds->string ? &ds->string[ds->length] : NULL; >>>> + size_t used = strftime_msec(dest, avail, template, &tm); >>>> if (used) { >>>> ds->length += used; >>>> return; >>> >>> The code looks OK to me. However, calling strftime_msec(NULL, 0,...) >>> once if the dynamic string is empty seems to me a bit obfuscated. >>> >>> I would personally just add: >>> >>> if (!ds->string) { >>> ds_reserve(ds, 64); >>> } >>> >>> before the loop to mentally get rid of that corner case. >> >> Sure, that's fine too, I have no preference either way. Ilya, what do >> you think, does this need a v2? > > Yeah, the ds_reserve() seems cleaner. We don't really need to > check for !ds->string before calling it though, IIUC. > > With that we may also remove the check while calculating 'avail'.
Done, thanks for the suggestions. I posted v2: dynamic-string: Fix undefined behavior due to offsetting null pointer. Thanks, Dumitru > > Best regards, Ilya Maximets. > >> >>> >>> In any case: >>> >>> Acked-by: Adrian Moreno <[email protected]> >>> >> >> Thanks for the review! >> > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
