On Mon, Oct 17, 2011 at 6:49 PM, Philip Anil-QBW348 <anil.philip@xxxxxxxxxxxxxxxxxxxxx> wrote: > -----Original Message----- > From: Daniel Baluta [mailto:daniel.baluta@xxxxxxxxx] > Sent: Saturday, October 15, 2011 3:34 AM > To: Philip Anil-QBW348 > Cc: kernelnewbies@xxxxxxxxxxxxxxxxx > Subject: Re: Getting 'bad file number' error writing to device driver > > On Sat, Oct 15, 2011 at 2:42 AM, Philip Anil-QBW348 > <anil.philip@xxxxxxxxxxxxxxxxxxxxx> wrote: >> I am calling the driver from an Android program (OMAP4/Blaze). It calls a >> c++ program via JNI which then calls the device driver. >> Someone suggested it might be a permissions problem - the program is running >> in user mode. >> >> on Blaze board, /system/bin >> # ls -l >> -rwxrwxrwx system system 7636 2011-09-30 03:53 mydriver >> >> Will strace still be useful? >> In general, in Linux, how does one enable a user program to call a custom >> device driver? > > Please don't top post! :) > > strace will be useful to check the parameters for open, write system calls. > > EBADF fd is not a valid file descriptor or is not open for writing. > Ok, so either open fails, or you don't have the permission to write > into /dev/mydriver file. > > ------ > I apologize for 'top-posting' (I did not know that was undesirable - most email clients and also Google newsgroups put one's reply at the top.). > Yes, the /dev/mydriver had permissions 600. I did a chmod to 666 and it worked. > I am performing security testing and want to see if a program running in user mode can elevate its privileges to call the device driver which has permissions 600. > Any ideas how it can? > Anil Maybe setuid bit can help you ([1]). When this bit is set, a certain program can run with the privileges of its owner. thanks, Daniel. [1] http://en.wikipedia.org/wiki/Setuid _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
