[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH for-4.15] tools/xenstored: liveupdate: Increase the maximum number of parameters
On 05.03.21 15:46, Ian Jackson wrote: Jürgen Groß writes ("Re: [PATCH for-4.15] tools/xenstored: liveupdate: Increase the maximum number of parameters"):On 05.03.21 15:37, Ian Jackson wrote:Jürgen Groß writes ("Re: [PATCH for-4.15] tools/xenstored: liveupdate: Increase the maximum number of parameters"):This is the max number of 0 delimited string parameters. Especially the stubdom case needs a binary blob (with length, of course) as parameter, and the number of 0 bytes in this data is just limited by the allowed payload length. See the comment in line 111 of xenstored_control.c.AFAICT this "live-update" command is variadic. So why is this parameter set here it all then ?In order to avoid allocating an array for 4000 arguments when there are only 5 which need to be treated as strings.So this parameter is doing two jobs: 1. enabling non-variadic commands to take binary input; 2. preventing variadic commands from allocating unbounded memory. The problem with this is that in case 1 exceeding the value is normal and the final argument is binary data; whereas in case 2 glomming together the arguments together with zeroes is wrong and potentially hazrdous. I suggest we solve problem 2 by imposing a higher fixed (for all commands, variadic or not) limit (20 or something) which causes errors when exceeded, rather than silent argument misinterpretation. Patches welcome. Juergen Attachment:
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