What prevents device files from being executed?

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I'm writing a kernel character device driver for which I've implemented the fops.read, and the FIONREAD (0x541B) ioctl. The data returned by read is an ELF executable. ls -l confirms that the device has r-x permissions, and both of the following commands allow me to execute the contained ELF binary:



# cp /dev/foo0 /tmp/bar && /tmp/bar
-or-
# cat /dev/foo0 > /tmp/bar && /tmp/bar
foo_open
foo_ioctl 0x0000541B
foo_read size=131072 off=0
foo_ioctl 0x0000541B
foo_read size=131072 off=13096
foo_release
Hello from /tmp/bar!
...


Note that the kernel messages indicate the various driver messages that are called. When I try to run the device directly, however, I get an error:



# /dev/foo0
foo_open
foo_release
/bin/sh: 6: /dev/foo0: Permission denied


What check might be causing the permissions error, and is it possible to override it without fundamentally breaking linux? I'm using the 4.18.3 kernel with a minimal sysroot image.






permissions linux-kernel devices






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    I'm writing a kernel character device driver for which I've implemented the fops.read, and the FIONREAD (0x541B) ioctl. The data returned by read is an ELF executable. ls -l confirms that the device has r-x permissions, and both of the following commands allow me to execute the contained ELF binary:



    # cp /dev/foo0 /tmp/bar && /tmp/bar
    -or-
    # cat /dev/foo0 > /tmp/bar && /tmp/bar
    foo_open
    foo_ioctl 0x0000541B
    foo_read size=131072 off=0
    foo_ioctl 0x0000541B
    foo_read size=131072 off=13096
    foo_release
    Hello from /tmp/bar!
    ...


    Note that the kernel messages indicate the various driver messages that are called. When I try to run the device directly, however, I get an error:



    # /dev/foo0
    foo_open
    foo_release
    /bin/sh: 6: /dev/foo0: Permission denied


    What check might be causing the permissions error, and is it possible to override it without fundamentally breaking linux? I'm using the 4.18.3 kernel with a minimal sysroot image.






    permissions linux-kernel devices






    share







    New contributor




    MooseBoys is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.





















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      I'm writing a kernel character device driver for which I've implemented the fops.read, and the FIONREAD (0x541B) ioctl. The data returned by read is an ELF executable. ls -l confirms that the device has r-x permissions, and both of the following commands allow me to execute the contained ELF binary:



      # cp /dev/foo0 /tmp/bar && /tmp/bar
      -or-
      # cat /dev/foo0 > /tmp/bar && /tmp/bar
      foo_open
      foo_ioctl 0x0000541B
      foo_read size=131072 off=0
      foo_ioctl 0x0000541B
      foo_read size=131072 off=13096
      foo_release
      Hello from /tmp/bar!
      ...


      Note that the kernel messages indicate the various driver messages that are called. When I try to run the device directly, however, I get an error:



      # /dev/foo0
      foo_open
      foo_release
      /bin/sh: 6: /dev/foo0: Permission denied


      What check might be causing the permissions error, and is it possible to override it without fundamentally breaking linux? I'm using the 4.18.3 kernel with a minimal sysroot image.






      permissions linux-kernel devices






      share







      New contributor




      MooseBoys is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      I'm writing a kernel character device driver for which I've implemented the fops.read, and the FIONREAD (0x541B) ioctl. The data returned by read is an ELF executable. ls -l confirms that the device has r-x permissions, and both of the following commands allow me to execute the contained ELF binary:



      # cp /dev/foo0 /tmp/bar && /tmp/bar
      -or-
      # cat /dev/foo0 > /tmp/bar && /tmp/bar
      foo_open
      foo_ioctl 0x0000541B
      foo_read size=131072 off=0
      foo_ioctl 0x0000541B
      foo_read size=131072 off=13096
      foo_release
      Hello from /tmp/bar!
      ...


      Note that the kernel messages indicate the various driver messages that are called. When I try to run the device directly, however, I get an error:



      # /dev/foo0
      foo_open
      foo_release
      /bin/sh: 6: /dev/foo0: Permission denied


      What check might be causing the permissions error, and is it possible to override it without fundamentally breaking linux? I'm using the 4.18.3 kernel with a minimal sysroot image.






      permissions linux-kernel devices




      permissions linux-kernel devices





      share







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      MooseBoys is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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