• Xiaochen Wang's avatar
    scripts/kallsyms.c: fix potential segfault · e0a04b11
    Xiaochen Wang authored
    Description:
    This bug hardly appears during real kernel compiling,
     because the vmlinux symbols table is huge.
    
    But we can still catch it under strict condition , as follows.
       $ echo "c101b97b T do_fork" | ./scripts/kallsyms --all-symbols
       #include <asm/types.h>
       ......
       ......
       .globl kallsyms_token_table
               ALGN
       kallsyms_token_table:
       Segmentation fault (core dumped)
       $
    
    If symbols table is small, all entries in token_profit[0x10000] may
    decrease to 0 after several calls of compress_symbols() in optimize_result().
    In that case, find_best_token() always return 0 and
    best_table[i] is set to "\0\0" and best_table_len[i] is set to 2.
    
    As a result, expand_symbol(best_table[0]="\0\0", best_table_len[0]=2, buf)
    in write_src() will run in infinite recursion until stack overflows,
    causing segfault.
    
    This patch checks the find_best_token() return value. If all entries in
    token_profit[0x10000] become 0 according to return value, it breaks the loop
    in optimize_result().
    And expand_symbol() works well when best_table_len[i] is 0.
    Signed-off-by: default avatarXiaochen Wang <wangxiaochen0@gmail.com>
    Acked-by: default avatarPaulo Marques <pmarques@grupopie.com>
    Signed-off-by: default avatarMichal Marek <mmarek@suse.cz>
    e0a04b11
kallsyms.c 15.2 KB