migration: Fix parse_ramblock() on overwritten retvals

[PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Peter Xu 2 years, 3 months ago

It's possible that some errors can be overwritten with success retval later
on, and then ignored.  Always capture all errors and report.

Reported by Coverity 1522861, but actually I spot one more in the same
function.

Fixes: CID 1522861
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/ram.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index c844151ee9..d8bdb53a8f 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3888,6 +3888,8 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
         ret = qemu_ram_resize(block, length, &local_err);
         if (local_err) {
             error_report_err(local_err);
+            assert(ret < 0);
+            return ret;
         }
     }
     /* For postcopy we need to check hugepage sizes match */
@@ -3898,7 +3900,7 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
             error_report("Mismatched RAM page size %s "
                          "(local) %zd != %" PRId64, block->idstr,
                          block->page_size, remote_page_size);
-            ret = -EINVAL;
+            return -EINVAL;
         }
     }
     if (migrate_ignore_shared()) {
@@ -3908,7 +3910,7 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
             error_report("Mismatched GPAs for block %s "
                          "%" PRId64 "!= %" PRId64, block->idstr,
                          (uint64_t)addr, (uint64_t)block->mr->addr);
-            ret = -EINVAL;
+            return -EINVAL;
         }
     }
     ret = rdma_block_notification_handle(f, block->idstr);
-- 
2.41.0

Re: [PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Peter Maydell 2 years, 3 months ago

On Tue, 17 Oct 2023 at 21:40, Peter Xu <peterx@redhat.com> wrote:
>
> It's possible that some errors can be overwritten with success retval later
> on, and then ignored.  Always capture all errors and report.
>
> Reported by Coverity 1522861, but actually I spot one more in the same
> function.

The other one is CID 1522862, I think.

> Fixes: CID 1522861
> Signed-off-by: Peter Xu <peterx@redhat.com>

> ---
>  migration/ram.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index c844151ee9..d8bdb53a8f 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3888,6 +3888,8 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
>          ret = qemu_ram_resize(block, length, &local_err);
>          if (local_err) {
>              error_report_err(local_err);
> +            assert(ret < 0);

We usually don't bother asserting for this kind of "function
reports errors two ways" code.

> +            return ret;
>          }

thanks
-- PMM

Re: [PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Peter Xu 2 years, 3 months ago

On Thu, Oct 19, 2023 at 01:40:29PM +0100, Peter Maydell wrote:
> On Tue, 17 Oct 2023 at 21:40, Peter Xu <peterx@redhat.com> wrote:
> >
> > It's possible that some errors can be overwritten with success retval later
> > on, and then ignored.  Always capture all errors and report.
> >
> > Reported by Coverity 1522861, but actually I spot one more in the same
> > function.
> 
> The other one is CID 1522862, I think.

Yes..

> 
> > Fixes: CID 1522861
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> 
> > ---
> >  migration/ram.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/migration/ram.c b/migration/ram.c
> > index c844151ee9..d8bdb53a8f 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -3888,6 +3888,8 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
> >          ret = qemu_ram_resize(block, length, &local_err);
> >          if (local_err) {
> >              error_report_err(local_err);
> > +            assert(ret < 0);
> 
> We usually don't bother asserting for this kind of "function
> reports errors two ways" code.

Juan, please feel free to drop the assert() if it's in the queue.

After this one lands, I'll send a patch to remove qemu_ram_resize retval
and only rely on Error*.

Thanks,

-- 
Peter Xu

Re: [PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Juan Quintela 2 years, 3 months ago

Peter Xu <peterx@redhat.com> wrote:
> It's possible that some errors can be overwritten with success retval later
> on, and then ignored.  Always capture all errors and report.
>
> Reported by Coverity 1522861, but actually I spot one more in the same
> function.
>
> Fixes: CID 1522861
> Signed-off-by: Peter Xu <peterx@redhat.com>


Reviewed-by: Juan Quintela <quintela@redhat.com>

queued.

Re: [PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Juan Quintela 2 years, 3 months ago

Peter Xu <peterx@redhat.com> wrote:
> It's possible that some errors can be overwritten with success retval later
> on, and then ignored.  Always capture all errors and report.
>
> Reported by Coverity 1522861, but actually I spot one more in the same
> function.
>
> Fixes: CID 1522861
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  migration/ram.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index c844151ee9..d8bdb53a8f 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3888,6 +3888,8 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
>          ret = qemu_ram_resize(block, length, &local_err);
>          if (local_err) {
>              error_report_err(local_err);
> +            assert(ret < 0);
> +            return ret;

I hate that assert.  If you really want that:


         if (ret < 0) {
            error_report_err(local_err);
            assert(ret < 0);
            return ret;
         }

Rest of the patch looks ok.

Later, Juan.

Re: [PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Peter Xu 2 years, 3 months ago

On Wed, Oct 18, 2023 at 09:12:36AM +0200, Juan Quintela wrote:
> Peter Xu <peterx@redhat.com> wrote:
> > It's possible that some errors can be overwritten with success retval later
> > on, and then ignored.  Always capture all errors and report.
> >
> > Reported by Coverity 1522861, but actually I spot one more in the same
> > function.
> >
> > Fixes: CID 1522861
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> >  migration/ram.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/migration/ram.c b/migration/ram.c
> > index c844151ee9..d8bdb53a8f 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -3888,6 +3888,8 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
> >          ret = qemu_ram_resize(block, length, &local_err);
> >          if (local_err) {
> >              error_report_err(local_err);
> > +            assert(ret < 0);
> > +            return ret;
> 
> I hate that assert.  If you really want that:

Please have a look at qemu_ram_resize().  It only contains two error paths.

> 
> 
>          if (ret < 0) {
>             error_report_err(local_err);

This will be similar to above, if qemu_ram_resize() return <0 with
err==NULL, it'll crash in error_report_err() too.. at error_get_pretty().

>             assert(ret < 0);

This is not necessary.. if in this "if" section.  So we can drop it
(instead of assert it).

>             return ret;
>          }
> 
> Rest of the patch looks ok.

I tend to prefer just merging this.. but if you strongly prefer the other
way, I can drop the assert().  But then I'll prefer "return -EINVAL" rather
than "return ret", if you're fine with it.

Thanks,

-- 
Peter Xu

Re: [PATCH] migration: Fix parse_ramblock() on overwritten retvals

Posted by Fabiano Rosas 2 years, 3 months ago

Peter Xu <peterx@redhat.com> writes:

> It's possible that some errors can be overwritten with success retval later
> on, and then ignored.  Always capture all errors and report.
>
> Reported by Coverity 1522861, but actually I spot one more in the same
> function.
>
> Fixes: CID 1522861
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Fabiano Rosas <farosas@suse.de>