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From: Leon Romanovsky <leon@kernel.org>
To: Joe Perches <joe@perches.com>
Cc: rds-devel@oss.oracle.com, Arnd Bergmann <arnd@arndb.de>,
	linux-rdma@vger.kernel.org,
	Santosh Shilimkar <santosh.shilimkar@oracle.com>,
	linux-kernel@vger.kernel.org, Peilin Ye <yepeilin.cs@gmail.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	netdev@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	"David S. Miller" <davem@davemloft.net>,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get()
Date: Mon, 3 Aug 2020 07:58:40 +0300	[thread overview]
Message-ID: <20200803045840.GM75549@unreal> (raw)
In-Reply-To: <60584f4c0303106b42463ddcfb108ec4a1f0b705.camel@perches.com>

On Sun, Aug 02, 2020 at 03:45:40PM -0700, Joe Perches wrote:
> On Sun, 2020-08-02 at 19:28 -0300, Jason Gunthorpe wrote:
> > On Sun, Aug 02, 2020 at 03:23:58PM -0700, Joe Perches wrote:
> > > On Sun, 2020-08-02 at 19:10 -0300, Jason Gunthorpe wrote:
> > > > On Sat, Aug 01, 2020 at 08:38:33AM +0300, Leon Romanovsky wrote:
> > > >
> > > > > I'm using {} instead of {0} because of this GCC bug.
> > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
> > > >
> > > > This is why the {} extension exists..
> > >
> > > There is no guarantee that the gcc struct initialization {}
> > > extension also zeros padding.
> >
> > We just went over this. Yes there is, C11 requires it.
>
> c11 is not c90.  The kernel uses c90.

It is not accurate, kernel uses gnu89 dialect, which is C90 with some
C99 features [1]. In our case, we rely on GCC extension {} that doesn't
contradict standart [2] and fills holes with zeros too.

[1] Makefile:500
   496 KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
   497                    -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
   498                    -Werror=implicit-function-declaration -Werror=implicit-int \
   499                    -Wno-format-security \
   500                    -std=gnu89

[2] From GCC:
https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
"When a base standard is specified, the compiler accepts all programs
following that standard plus those using GNU extensions that do not
contradict it."

Thanks

>
>
>
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

WARNING: multiple messages have this Message-ID (diff)
From: Leon Romanovsky <leon@kernel.org>
To: Joe Perches <joe@perches.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Peilin Ye <yepeilin.cs@gmail.com>,
	Santosh Shilimkar <santosh.shilimkar@oracle.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
	rds-devel@oss.oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get()
Date: Mon, 3 Aug 2020 07:58:40 +0300	[thread overview]
Message-ID: <20200803045840.GM75549@unreal> (raw)
In-Reply-To: <60584f4c0303106b42463ddcfb108ec4a1f0b705.camel@perches.com>

On Sun, Aug 02, 2020 at 03:45:40PM -0700, Joe Perches wrote:
> On Sun, 2020-08-02 at 19:28 -0300, Jason Gunthorpe wrote:
> > On Sun, Aug 02, 2020 at 03:23:58PM -0700, Joe Perches wrote:
> > > On Sun, 2020-08-02 at 19:10 -0300, Jason Gunthorpe wrote:
> > > > On Sat, Aug 01, 2020 at 08:38:33AM +0300, Leon Romanovsky wrote:
> > > >
> > > > > I'm using {} instead of {0} because of this GCC bug.
> > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
> > > >
> > > > This is why the {} extension exists..
> > >
> > > There is no guarantee that the gcc struct initialization {}
> > > extension also zeros padding.
> >
> > We just went over this. Yes there is, C11 requires it.
>
> c11 is not c90.  The kernel uses c90.

It is not accurate, kernel uses gnu89 dialect, which is C90 with some
C99 features [1]. In our case, we rely on GCC extension {} that doesn't
contradict standart [2] and fills holes with zeros too.

[1] Makefile:500
   496 KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
   497                    -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
   498                    -Werror=implicit-function-declaration -Werror=implicit-int \
   499                    -Wno-format-security \
   500                    -std=gnu89

[2] From GCC:
https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
"When a base standard is specified, the compiler accepts all programs
following that standard plus those using GNU extensions that do not
contradict it."

Thanks

>
>
>

  reply	other threads:[~2020-08-03  4:58 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 19:20 [Linux-kernel-mentees] [PATCH net] rds: Prevent kernel-infoleak in rds_notify_queue_get() Peilin Ye
2020-07-30 19:20 ` Peilin Ye
2020-07-30 19:29 ` santosh.shilimkar
2020-07-30 19:29   ` santosh.shilimkar
2020-07-31  4:53 ` Leon Romanovsky
2020-07-31  4:53   ` Leon Romanovsky
2020-07-31  5:33   ` Greg Kroah-Hartman
2020-07-31  5:33     ` Greg Kroah-Hartman
2020-07-31  5:33     ` Greg Kroah-Hartman
2020-07-31  5:33       ` Greg Kroah-Hartman
2020-07-31  6:29       ` Andy Shevchenko
2020-07-31  7:00         ` Leon Romanovsky
2020-07-31  7:00           ` Leon Romanovsky
2020-07-31  7:05           ` Andy Shevchenko
2020-07-31  7:05             ` Andy Shevchenko
2020-07-31 14:04       ` Jason Gunthorpe
2020-07-31 14:04         ` Jason Gunthorpe
2020-07-31 14:21         ` Greg Kroah-Hartman
2020-07-31 14:21           ` Greg Kroah-Hartman
2020-07-31 14:36           ` Jason Gunthorpe
2020-07-31 14:36             ` Jason Gunthorpe
2020-07-31 17:19             ` Greg Kroah-Hartman
2020-07-31 17:19               ` Greg Kroah-Hartman
2020-07-31 18:27               ` Jason Gunthorpe
2020-07-31 18:27                 ` Jason Gunthorpe
2020-08-01  8:00                 ` Dan Carpenter
2020-08-01  8:00                   ` Dan Carpenter
2020-08-01 14:40                   ` Jason Gunthorpe
2020-08-01 14:40                     ` Jason Gunthorpe
2020-08-03  9:34                     ` Dan Carpenter
2020-08-03  9:34                       ` Dan Carpenter
2020-08-01  5:38               ` Leon Romanovsky
2020-08-01  5:38                 ` Leon Romanovsky
2020-08-02 22:10                 ` Jason Gunthorpe
2020-08-02 22:10                   ` Jason Gunthorpe
2020-08-02 22:23                   ` Joe Perches
2020-08-02 22:23                     ` Joe Perches
2020-08-02 22:28                     ` Jason Gunthorpe
2020-08-02 22:28                       ` Jason Gunthorpe
2020-08-02 22:45                       ` Joe Perches
2020-08-02 22:45                         ` Joe Perches
2020-08-03  4:58                         ` Leon Romanovsky [this message]
2020-08-03  4:58                           ` Leon Romanovsky
2020-08-03 23:06                         ` Jason Gunthorpe
2020-08-03 23:06                           ` Jason Gunthorpe
2020-08-08 22:57                           ` Jack Leadford
2020-08-08 22:57                             ` Jack Leadford
2020-08-09  7:04                             ` Leon Romanovsky
2020-08-09  7:04                               ` Leon Romanovsky
2020-08-14 17:07                             ` Jason Gunthorpe
2020-08-14 17:07                               ` Jason Gunthorpe
2020-07-31  6:31   ` Andy Shevchenko
2020-07-31  9:59   ` Dan Carpenter
2020-07-31  9:59     ` Dan Carpenter
2020-07-31 11:14     ` Håkon Bugge
2020-07-31 11:14       ` Håkon Bugge
2020-07-31 11:59       ` Greg Kroah-Hartman
2020-07-31 11:59         ` Greg Kroah-Hartman
2020-07-31 12:03         ` Håkon Bugge
2020-07-31 12:03           ` Håkon Bugge
2020-07-31 23:54 ` David Miller
2020-07-31 23:54   ` David Miller

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