[PATCH] lib/mempool : rte_mempool_avail_count, fixing return bigger than mempool size

[Morten Brørup]

From: Yasin CANER [mailto:yasinncaner at gmail.com] 
Sent: Thursday, 18 May 2023 10.37



Hello, 

 

I found a second free command in my code and removed it. David pointed to the right .

 

MB: Good to hear.

 

On the other hand, do you think we need to avoid miscalculations? Is it better to patch it or not?

 

MB: There is no bug in the library, so no need to patch it. The returned value was a consequence of using the library incorrectly (freeing twice).

 

or it needs to be aware of the second free command. 

 

Sharing more information about env.

 

# ethtool -i mgmt
driver: virtio_net
version: 1.0.0
firmware-version:
expansion-rom-version:
bus-info: 0000:00:03.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no

 

NAME="Ubuntu"
VERSION="20.04.4 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.4 LTS"
VERSION_ID="20.04"

 

Linux spgw-dpdk 5.4.0-146-generic #163-Ubuntu SMP Fri Mar 17 18:26:02 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

 

 

 

Best regards.

 

Morten Brørup <mb at smartsharesystems.com>, 17 May 2023 Çar, 15:23 tarihinde şunu yazdı:

	> From: David Marchand [mailto:david.marchand at redhat.com]
	> Sent: Wednesday, 17 May 2023 13.53
	> 
	> On Wed, May 17, 2023 at 11:05 AM Morten Brørup <mb at smartsharesystems.com>
	> wrote:
	> > > On Tue, 16 May 2023 13:41:46 +0000
	> > > Yasin CANER <yasinncaner at gmail.com> wrote:
	> > >
	> > > > From: Yasin CANER <yasin.caner at ulakhaberlesme.com.tr>
	> > > >
	> > > > after a while working rte_mempool_avail_count function returns bigger
	> > > > than mempool size that cause miscalculation rte_mempool_in_use_count.
	> > > >
	> > > > it helps to avoid miscalculation rte_mempool_in_use_count.
	> 
	> Is this issue reproduced with an application of the reporter, or a
	> DPDK in-tree application?
	> 
	> 
	> > > >
	> > > > Bugzilla ID: 1229
	> > > >
	> > > > Signed-off-by: Yasin CANER <yasin.caner at ulakhaberlesme.com.tr>
	> > >
	> > > An alternative that avoids some code duplication.
	> > >
	> > > diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
	> > > index cf5dea2304a7..2406b112e7b0 100644
	> > > --- a/lib/mempool/rte_mempool.c
	> > > +++ b/lib/mempool/rte_mempool.c
	> > > @@ -1010,7 +1010,7 @@ rte_mempool_avail_count(const struct rte_mempool
	> > > *mp)
	> > >         count = rte_mempool_ops_get_count(mp);
	> > >
	> > >         if (mp->cache_size == 0)
	> > > -               return count;
	> > > +               goto exit;
	> >
	> > This bug can only occur here (i.e. with cache_size==0) if
	> rte_mempool_ops_get_count() returns an incorrect value. The bug should be
	> fixed there instead.
	> >
	> >
	> >
	> > MB (continued): The bug must be in the underlying mempool driver. I took a
	> look at the ring and stack drivers, and they seem fine.
	> 
	> Or it could indicate a double free (or equivalent) issue from the
	> application (either through direct call to mempool API, or indirectly
	> like sending/freeing an already sent/freed packet for example).
	
	Good point, David.
	
	@Yasin, if you build DPDK and your application with RTE_LIBRTE_MEMPOOL_DEBUG set in config/rte_config.h, the mempool cookies should catch any double frees.

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