| Message ID | 20240429191426.2327225-4-vsementsov@yandex-team.ru (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | migration: do not exit on incoming failure | expand |
On Mon, Apr 29, 2024 at 10:14:24PM +0300, Vladimir Sementsov-Ogievskiy wrote: > It's bad idea to leave critical section with error object freed, but > s->error still set, this theoretically may lead to use-after-free > crash. Let's avoid it. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> > --- > migration/migration.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index 0d26db47f7..58fd5819bc 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -732,9 +732,19 @@ static void process_incoming_migration_bh(void *opaque) > migration_incoming_state_destroy(); > } > > +static void migrate_error_free(MigrationState *s) > +{ > + QEMU_LOCK_GUARD(&s->error_mutex); > + if (s->error) { > + error_free(s->error); > + s->error = NULL; > + } > +} > + > static void coroutine_fn > process_incoming_migration_co(void *opaque) > { > + MigrationState *s = migrate_get_current(); > MigrationIncomingState *mis = migration_incoming_get_current(); > PostcopyState ps; > int ret; > @@ -779,11 +789,9 @@ process_incoming_migration_co(void *opaque) > } > > if (ret < 0) { > - MigrationState *s = migrate_get_current(); > - > if (migrate_has_error(s)) { > WITH_QEMU_LOCK_GUARD(&s->error_mutex) { > - error_report_err(s->error); > + error_report_err(error_copy(s->error)); This looks like a bugfix, agreed. > } > } > error_report("load of migration failed: %s", strerror(-ret)); > @@ -801,6 +809,7 @@ fail: > MIGRATION_STATUS_FAILED); > migration_incoming_state_destroy(); > > + migrate_error_free(s); Would migration_incoming_state_destroy() be a better place? One thing weird is we actually reuses MigrationState*'s error for incoming too, but so far it looks ok as long as QEMU can't be both src & dst. Then calling migrate_error_free even in incoming_state_destroy() looks ok. This patch still looks like containing two changes. Better split them (or just fix the bug only)? Thanks, > exit(EXIT_FAILURE); > } > > @@ -1433,15 +1442,6 @@ bool migrate_has_error(MigrationState *s) > return qatomic_read(&s->error); > } > > -static void migrate_error_free(MigrationState *s) > -{ > - QEMU_LOCK_GUARD(&s->error_mutex); > - if (s->error) { > - error_free(s->error); > - s->error = NULL; > - } > -} > - > static void migrate_fd_error(MigrationState *s, const Error *error) > { > assert(s->to_dst_file == NULL); > -- > 2.34.1 >
On 29.04.24 22:32, Peter Xu wrote: > On Mon, Apr 29, 2024 at 10:14:24PM +0300, Vladimir Sementsov-Ogievskiy wrote: >> It's bad idea to leave critical section with error object freed, but >> s->error still set, this theoretically may lead to use-after-free >> crash. Let's avoid it. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> >> --- >> migration/migration.c | 24 ++++++++++++------------ >> 1 file changed, 12 insertions(+), 12 deletions(-) >> >> diff --git a/migration/migration.c b/migration/migration.c >> index 0d26db47f7..58fd5819bc 100644 >> --- a/migration/migration.c >> +++ b/migration/migration.c >> @@ -732,9 +732,19 @@ static void process_incoming_migration_bh(void *opaque) >> migration_incoming_state_destroy(); >> } >> >> +static void migrate_error_free(MigrationState *s) >> +{ >> + QEMU_LOCK_GUARD(&s->error_mutex); >> + if (s->error) { >> + error_free(s->error); >> + s->error = NULL; >> + } >> +} >> + >> static void coroutine_fn >> process_incoming_migration_co(void *opaque) >> { >> + MigrationState *s = migrate_get_current(); >> MigrationIncomingState *mis = migration_incoming_get_current(); >> PostcopyState ps; >> int ret; >> @@ -779,11 +789,9 @@ process_incoming_migration_co(void *opaque) >> } >> >> if (ret < 0) { >> - MigrationState *s = migrate_get_current(); >> - >> if (migrate_has_error(s)) { >> WITH_QEMU_LOCK_GUARD(&s->error_mutex) { >> - error_report_err(s->error); >> + error_report_err(error_copy(s->error)); > > This looks like a bugfix, agreed. > >> } >> } >> error_report("load of migration failed: %s", strerror(-ret)); >> @@ -801,6 +809,7 @@ fail: >> MIGRATION_STATUS_FAILED); >> migration_incoming_state_destroy(); >> >> + migrate_error_free(s); > > Would migration_incoming_state_destroy() be a better place? Hmm. But we want to call migration_incoming_state_destroy() in case when exit-on-error=false too. And in this case we want to keep the error for further query-migrate commands. > > One thing weird is we actually reuses MigrationState*'s error for incoming > too, but so far it looks ok as long as QEMU can't be both src & dst. Then > calling migrate_error_free even in incoming_state_destroy() looks ok. > > This patch still looks like containing two changes. Better split them (or > just fix the bug only)? > > Thanks, > >> exit(EXIT_FAILURE); >> } >> >> @@ -1433,15 +1442,6 @@ bool migrate_has_error(MigrationState *s) >> return qatomic_read(&s->error); >> } >> >> -static void migrate_error_free(MigrationState *s) >> -{ >> - QEMU_LOCK_GUARD(&s->error_mutex); >> - if (s->error) { >> - error_free(s->error); >> - s->error = NULL; >> - } >> -} >> - >> static void migrate_fd_error(MigrationState *s, const Error *error) >> { >> assert(s->to_dst_file == NULL); >> -- >> 2.34.1 >> >
On 30.04.24 11:06, Vladimir Sementsov-Ogievskiy wrote: > On 29.04.24 22:32, Peter Xu wrote: >> On Mon, Apr 29, 2024 at 10:14:24PM +0300, Vladimir Sementsov-Ogievskiy wrote: >>> It's bad idea to leave critical section with error object freed, but >>> s->error still set, this theoretically may lead to use-after-free >>> crash. Let's avoid it. >>> >>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> >>> --- >>> migration/migration.c | 24 ++++++++++++------------ >>> 1 file changed, 12 insertions(+), 12 deletions(-) >>> >>> diff --git a/migration/migration.c b/migration/migration.c >>> index 0d26db47f7..58fd5819bc 100644 >>> --- a/migration/migration.c >>> +++ b/migration/migration.c >>> @@ -732,9 +732,19 @@ static void process_incoming_migration_bh(void *opaque) >>> migration_incoming_state_destroy(); >>> } >>> +static void migrate_error_free(MigrationState *s) >>> +{ >>> + QEMU_LOCK_GUARD(&s->error_mutex); >>> + if (s->error) { >>> + error_free(s->error); >>> + s->error = NULL; >>> + } >>> +} >>> + >>> static void coroutine_fn >>> process_incoming_migration_co(void *opaque) >>> { >>> + MigrationState *s = migrate_get_current(); >>> MigrationIncomingState *mis = migration_incoming_get_current(); >>> PostcopyState ps; >>> int ret; >>> @@ -779,11 +789,9 @@ process_incoming_migration_co(void *opaque) >>> } >>> if (ret < 0) { >>> - MigrationState *s = migrate_get_current(); >>> - >>> if (migrate_has_error(s)) { >>> WITH_QEMU_LOCK_GUARD(&s->error_mutex) { >>> - error_report_err(s->error); >>> + error_report_err(error_copy(s->error)); >> >> This looks like a bugfix, agreed. >> >>> } >>> } >>> error_report("load of migration failed: %s", strerror(-ret)); >>> @@ -801,6 +809,7 @@ fail: >>> MIGRATION_STATUS_FAILED); >>> migration_incoming_state_destroy(); >>> + migrate_error_free(s); >> >> Would migration_incoming_state_destroy() be a better place? > > Hmm. But we want to call migration_incoming_state_destroy() in case when exit-on-error=false too. And in this case we want to keep the error for further query-migrate commands. Actually, I think we shouldn't care about freeing the error for exit() case. I think, we skip a lot of other cleanups which we normally do in main() in case of this exit(). > >> >> One thing weird is we actually reuses MigrationState*'s error for incoming >> too, but so far it looks ok as long as QEMU can't be both src & dst. Then >> calling migrate_error_free even in incoming_state_destroy() looks ok. >> >> This patch still looks like containing two changes. Better split them (or >> just fix the bug only)? >> >> Thanks, >> >>> exit(EXIT_FAILURE); >>> } >>> @@ -1433,15 +1442,6 @@ bool migrate_has_error(MigrationState *s) >>> return qatomic_read(&s->error); >>> } >>> -static void migrate_error_free(MigrationState *s) >>> -{ >>> - QEMU_LOCK_GUARD(&s->error_mutex); >>> - if (s->error) { >>> - error_free(s->error); >>> - s->error = NULL; >>> - } >>> -} >>> - >>> static void migrate_fd_error(MigrationState *s, const Error *error) >>> { >>> assert(s->to_dst_file == NULL); >>> -- >>> 2.34.1 >>> >> >
On 30.04.24 11:09, Vladimir Sementsov-Ogievskiy wrote: > On 30.04.24 11:06, Vladimir Sementsov-Ogievskiy wrote: >> On 29.04.24 22:32, Peter Xu wrote: >>> On Mon, Apr 29, 2024 at 10:14:24PM +0300, Vladimir Sementsov-Ogievskiy wrote: >>>> It's bad idea to leave critical section with error object freed, but >>>> s->error still set, this theoretically may lead to use-after-free >>>> crash. Let's avoid it. >>>> >>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> >>>> --- >>>> migration/migration.c | 24 ++++++++++++------------ >>>> 1 file changed, 12 insertions(+), 12 deletions(-) >>>> >>>> diff --git a/migration/migration.c b/migration/migration.c >>>> index 0d26db47f7..58fd5819bc 100644 >>>> --- a/migration/migration.c >>>> +++ b/migration/migration.c >>>> @@ -732,9 +732,19 @@ static void process_incoming_migration_bh(void *opaque) >>>> migration_incoming_state_destroy(); >>>> } >>>> +static void migrate_error_free(MigrationState *s) >>>> +{ >>>> + QEMU_LOCK_GUARD(&s->error_mutex); >>>> + if (s->error) { >>>> + error_free(s->error); >>>> + s->error = NULL; >>>> + } >>>> +} >>>> + >>>> static void coroutine_fn >>>> process_incoming_migration_co(void *opaque) >>>> { >>>> + MigrationState *s = migrate_get_current(); >>>> MigrationIncomingState *mis = migration_incoming_get_current(); >>>> PostcopyState ps; >>>> int ret; >>>> @@ -779,11 +789,9 @@ process_incoming_migration_co(void *opaque) >>>> } >>>> if (ret < 0) { >>>> - MigrationState *s = migrate_get_current(); >>>> - >>>> if (migrate_has_error(s)) { >>>> WITH_QEMU_LOCK_GUARD(&s->error_mutex) { >>>> - error_report_err(s->error); >>>> + error_report_err(error_copy(s->error)); >>> >>> This looks like a bugfix, agreed. >>> >>>> } >>>> } >>>> error_report("load of migration failed: %s", strerror(-ret)); >>>> @@ -801,6 +809,7 @@ fail: >>>> MIGRATION_STATUS_FAILED); >>>> migration_incoming_state_destroy(); >>>> + migrate_error_free(s); >>> >>> Would migration_incoming_state_destroy() be a better place? >> >> Hmm. But we want to call migration_incoming_state_destroy() in case when exit-on-error=false too. And in this case we want to keep the error for further query-migrate commands. > > Actually, I think we shouldn't care about freeing the error for exit() case. I think, we skip a lot of other cleanups which we normally do in main() in case of this exit(). > Or, just do the simplest fix of potential use-after-free, and don't care: WITH_QEMU_LOCK_GUARD(&s->error_mutex) { error_report_err(s->error); s->error = NULL; } - I'll send v6 with it. >> >>> >>> One thing weird is we actually reuses MigrationState*'s error for incoming >>> too, but so far it looks ok as long as QEMU can't be both src & dst. Then >>> calling migrate_error_free even in incoming_state_destroy() looks ok. >>> >>> This patch still looks like containing two changes. Better split them (or >>> just fix the bug only)? >>> >>> Thanks, >>> >>>> exit(EXIT_FAILURE); >>>> } >>>> @@ -1433,15 +1442,6 @@ bool migrate_has_error(MigrationState *s) >>>> return qatomic_read(&s->error); >>>> } >>>> -static void migrate_error_free(MigrationState *s) >>>> -{ >>>> - QEMU_LOCK_GUARD(&s->error_mutex); >>>> - if (s->error) { >>>> - error_free(s->error); >>>> - s->error = NULL; >>>> - } >>>> -} >>>> - >>>> static void migrate_fd_error(MigrationState *s, const Error *error) >>>> { >>>> assert(s->to_dst_file == NULL); >>>> -- >>>> 2.34.1 >>>> >>> >> >
diff --git a/migration/migration.c b/migration/migration.c index 0d26db47f7..58fd5819bc 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -732,9 +732,19 @@ static void process_incoming_migration_bh(void *opaque) migration_incoming_state_destroy(); } +static void migrate_error_free(MigrationState *s) +{ + QEMU_LOCK_GUARD(&s->error_mutex); + if (s->error) { + error_free(s->error); + s->error = NULL; + } +} + static void coroutine_fn process_incoming_migration_co(void *opaque) { + MigrationState *s = migrate_get_current(); MigrationIncomingState *mis = migration_incoming_get_current(); PostcopyState ps; int ret; @@ -779,11 +789,9 @@ process_incoming_migration_co(void *opaque) } if (ret < 0) { - MigrationState *s = migrate_get_current(); - if (migrate_has_error(s)) { WITH_QEMU_LOCK_GUARD(&s->error_mutex) { - error_report_err(s->error); + error_report_err(error_copy(s->error)); } } error_report("load of migration failed: %s", strerror(-ret)); @@ -801,6 +809,7 @@ fail: MIGRATION_STATUS_FAILED); migration_incoming_state_destroy(); + migrate_error_free(s); exit(EXIT_FAILURE); } @@ -1433,15 +1442,6 @@ bool migrate_has_error(MigrationState *s) return qatomic_read(&s->error); } -static void migrate_error_free(MigrationState *s) -{ - QEMU_LOCK_GUARD(&s->error_mutex); - if (s->error) { - error_free(s->error); - s->error = NULL; - } -} - static void migrate_fd_error(MigrationState *s, const Error *error) { assert(s->to_dst_file == NULL);
It's bad idea to leave critical section with error object freed, but s->error still set, this theoretically may lead to use-after-free crash. Let's avoid it. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> --- migration/migration.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)