• Schichan Nicolas's avatar
    ARM: 7598/1: net: bpf_jit_32: fix sp-relative load/stores offsets. · fe15f3f1
    Schichan Nicolas authored
    The offset must be multiplied by 4 to be sure to access the correct
    32bit word in the stack scratch space.
    
    For instance, a store at scratch memory cell #1 was generating the
    following:
    
    st	r4, [sp, #1]
    
    While the correct code for this is:
    
    st	r4, [sp, #4]
    
    To reproduce the bug (assuming your system has a NIC with the mac
    address 52:54:00:12:34:56):
    
    echo 0 > /proc/sys/net/core/bpf_jit_enable
    tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \
    	== -0x3AA" # this will capture packets as expected
    
    echo 1 > /proc/sys/net/core/bpf_jit_enable
    tcpdump -ni eth0 "ether[1] + ether[2] - ether[3] * ether[4] - ether[5] \
    	== -0x3AA" # this will not.
    
    This bug was present since the original inclusion of bpf_jit for ARM
    (ddecdfce
    
    : ARM: 7259/3: net: JIT compiler for packet filters).
    Signed-off-by: default avatarNicolas Schichan <nschichan@freebox.fr>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    fe15f3f1