netdev - Re: [PATCH v6 net-next 11/15] net: catch errors from dev_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6a6f5e835255a196f461b0e63a68b9bfa576ca1f.camel@kernel.org>
Date:   Mon, 11 Jan 2021 15:51:39 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Eric Dumazet <edumazet@...gle.com>,
        George McCollister <george.mccollister@...il.com>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Arnd Bergmann <arnd@...db.de>, Taehee Yoo <ap420073@...il.com>,
        Jiri Pirko <jiri@...nulli.us>, Florian Westphal <fw@...len.de>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Pravin B Shelar <pshelar@....org>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>
Subject: Re: [PATCH v6 net-next 11/15] net: catch errors from dev_get_stats

On Tue, 2021-01-12 at 01:15 +0200, Vladimir Oltean wrote:
> On Mon, Jan 11, 2021 at 02:54:50PM -0800, Saeed Mahameed wrote:
> > On Sat, 2021-01-09 at 19:26 +0200, Vladimir Oltean wrote:
> > > From: Vladimir Oltean <vladimir.oltean@....com>
> > > 
> > > dev_get_stats can now return error codes. Convert all remaining
> > > call
> > > sites to look at that error code and stop processing.
> > > 
> > > The effects of simulating a kernel error (returning -ENOMEM) upon
> > > existing programs or kernel interfaces:
> > > 
> > > - ifconfig and "cat /proc/net/dev" print up until the interface
> > > that
> > >   failed, and there they return:
> > > cat: read error: Cannot allocate memory
> > > 
> > > - ifstat and "ip -s -s link show":
> > > RTNETLINK answers: Cannot allocate memory
> > > Dump terminated
> > > 
> > > Some call sites are coming from a context that returns void
> > > (ethtool
> > > stats, workqueue context). So since we can't report to the upper
> > > layer,
> > > do the next best thing: print an error to the console.
> > > 
> > 
> > another concern, one buggy netdev driver in a system will cause
> > unnecessary global failures when reading stats via netlink/procfs
> > for
> > all the netdev in a netns, when other drivers will be happy to
> > report.
> > 
> > can't we just show a message in that driver's stats line about the
> > occurred err ? and show the normal stats line of all others ?
> 
> So you're worried that user space apps won't handle an error code
> when
> reading from a file, but you're not worried that they'll start
> scraping
> junk from procfs when we print this?
> 

both are equivalently concerning.
to avoid any user crashes, we can just toss failed netdevs out from the
output.

> cat /proc/net/dev
> Inter-
> |   Receive                                                |  Transmi
> t
>  face |bytes    packets errs drop fifo frame compressed
> multicast|bytes    packets errs drop fifo colls carrier compressed
>     lo:       0       0    0    0    0     0          0         0    
>     0       0    0    0    0     0       0          0
>  bond0: Cannot allocate memory
>  
> sit0:       0       0    0    0    0     0          0         0      
>   0       0    0    0    0     0       0          0