-----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 _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
