• Pavel Emelyanov's avatar
    binfmt_misc.c: avoid potential kernel stack overflow · 3a2e7f47
    Pavel Emelyanov authored
    This can be triggered with root help only, but...
    
    Register the ":text:E::txt::/root/cat.txt:' rule in binfmt_misc (by root) and
    try launching the cat.txt file (by anyone) :) The result is - the endless
    recursion in the load_misc_binary -> open_exec -> load_misc_binary chain and
    stack overflow.
    
    There's a similar problem with binfmt_script, and there's a sh_bang memner on
    linux_binprm structure to handle this, but simply raising this in binfmt_misc
    may break some setups when the interpreter of some misc binaries is a script.
    
    So the proposal is to turn sh_bang into a bit, add a new one (the misc_bang)
    and raise it in load_misc_binary.  After this, even if we set up the misc ->
    script -> misc loop for binfmts one of them will step on its own bang and
    exit.
    Signed-off-by: default avatarPavel Emelyanov <xemul@openvz.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    3a2e7f47
binfmt_script.c 2.72 KB