1. 29 1月, 2016 1 次提交
  2. 03 12月, 2015 1 次提交
    • A
      bpf: fix allocation warnings in bpf maps and integer overflow · 01b3f521
      Alexei Starovoitov 提交于
      For large map->value_size the user space can trigger memory allocation warnings like:
      WARNING: CPU: 2 PID: 11122 at mm/page_alloc.c:2989
      __alloc_pages_nodemask+0x695/0x14e0()
      Call Trace:
       [<     inline     >] __dump_stack lib/dump_stack.c:15
       [<ffffffff82743b56>] dump_stack+0x68/0x92 lib/dump_stack.c:50
       [<ffffffff81244ec9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:460
       [<ffffffff812450f9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:493
       [<     inline     >] __alloc_pages_slowpath mm/page_alloc.c:2989
       [<ffffffff81554e95>] __alloc_pages_nodemask+0x695/0x14e0 mm/page_alloc.c:3235
       [<ffffffff816188fe>] alloc_pages_current+0xee/0x340 mm/mempolicy.c:2055
       [<     inline     >] alloc_pages include/linux/gfp.h:451
       [<ffffffff81550706>] alloc_kmem_pages+0x16/0xf0 mm/page_alloc.c:3414
       [<ffffffff815a1c89>] kmalloc_order+0x19/0x60 mm/slab_common.c:1007
       [<ffffffff815a1cef>] kmalloc_order_trace+0x1f/0xa0 mm/slab_common.c:1018
       [<     inline     >] kmalloc_large include/linux/slab.h:390
       [<ffffffff81627784>] __kmalloc+0x234/0x250 mm/slub.c:3525
       [<     inline     >] kmalloc include/linux/slab.h:463
       [<     inline     >] map_update_elem kernel/bpf/syscall.c:288
       [<     inline     >] SYSC_bpf kernel/bpf/syscall.c:744
      
      To avoid never succeeding kmalloc with order >= MAX_ORDER check that
      elem->value_size and computed elem_size are within limits for both hash and
      array type maps.
      Also add __GFP_NOWARN to kmalloc(value_size | elem_size) to avoid OOM warnings.
      Note kmalloc(key_size) is highly unlikely to trigger OOM, since key_size <= 512,
      so keep those kmalloc-s as-is.
      
      Large value_size can cause integer overflows in elem_size and map.pages
      formulas, so check for that as well.
      
      Fixes: aaac3ba9 ("bpf: charge user for creation of BPF maps and programs")
      Reported-by: NDmitry Vyukov <dvyukov@google.com>
      Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      01b3f521
  3. 02 12月, 2015 1 次提交
    • D
      bpf, array: fix heap out-of-bounds access when updating elements · fbca9d2d
      Daniel Borkmann 提交于
      During own review but also reported by Dmitry's syzkaller [1] it has been
      noticed that we trigger a heap out-of-bounds access on eBPF array maps
      when updating elements. This happens with each map whose map->value_size
      (specified during map creation time) is not multiple of 8 bytes.
      
      In array_map_alloc(), elem_size is round_up(attr->value_size, 8) and
      used to align array map slots for faster access. However, in function
      array_map_update_elem(), we update the element as ...
      
      memcpy(array->value + array->elem_size * index, value, array->elem_size);
      
      ... where we access 'value' out-of-bounds, since it was allocated from
      map_update_elem() from syscall side as kmalloc(map->value_size, GFP_USER)
      and later on copied through copy_from_user(value, uvalue, map->value_size).
      Thus, up to 7 bytes, we can access out-of-bounds.
      
      Same could happen from within an eBPF program, where in worst case we
      access beyond an eBPF program's designated stack.
      
      Since 1be7f75d ("bpf: enable non-root eBPF programs") didn't hit an
      official release yet, it only affects priviledged users.
      
      In case of array_map_lookup_elem(), the verifier prevents eBPF programs
      from accessing beyond map->value_size through check_map_access(). Also
      from syscall side map_lookup_elem() only copies map->value_size back to
      user, so nothing could leak.
      
        [1] http://github.com/google/syzkaller
      
      Fixes: 28fbcfa0 ("bpf: add array type of eBPF maps")
      Reported-by: NDmitry Vyukov <dvyukov@google.com>
      Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
      Acked-by: NAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      fbca9d2d
  4. 27 10月, 2015 1 次提交
  5. 22 10月, 2015 1 次提交
    • A
      bpf: introduce bpf_perf_event_output() helper · a43eec30
      Alexei Starovoitov 提交于
      This helper is used to send raw data from eBPF program into
      special PERF_TYPE_SOFTWARE/PERF_COUNT_SW_BPF_OUTPUT perf_event.
      User space needs to perf_event_open() it (either for one or all cpus) and
      store FD into perf_event_array (similar to bpf_perf_event_read() helper)
      before eBPF program can send data into it.
      
      Today the programs triggered by kprobe collect the data and either store
      it into the maps or print it via bpf_trace_printk() where latter is the debug
      facility and not suitable to stream the data. This new helper replaces
      such bpf_trace_printk() usage and allows programs to have dedicated
      channel into user space for post-processing of the raw data collected.
      Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a43eec30
  6. 13 10月, 2015 1 次提交
    • A
      bpf: charge user for creation of BPF maps and programs · aaac3ba9
      Alexei Starovoitov 提交于
      since eBPF programs and maps use kernel memory consider it 'locked' memory
      from user accounting point of view and charge it against RLIMIT_MEMLOCK limit.
      This limit is typically set to 64Kbytes by distros, so almost all
      bpf+tracing programs would need to increase it, since they use maps,
      but kernel charges maximum map size upfront.
      For example the hash map of 1024 elements will be charged as 64Kbyte.
      It's inconvenient for current users and changes current behavior for root,
      but probably worth doing to be consistent root vs non-root.
      
      Similar accounting logic is done by mmap of perf_event.
      Signed-off-by: NAlexei Starovoitov <ast@plumgrid.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      aaac3ba9
  7. 05 10月, 2015 1 次提交
  8. 10 8月, 2015 2 次提交
  9. 31 5月, 2015 1 次提交
  10. 22 5月, 2015 1 次提交
    • A
      bpf: allow bpf programs to tail-call other bpf programs · 04fd61ab
      Alexei Starovoitov 提交于
      introduce bpf_tail_call(ctx, &jmp_table, index) helper function
      which can be used from BPF programs like:
      int bpf_prog(struct pt_regs *ctx)
      {
        ...
        bpf_tail_call(ctx, &jmp_table, index);
        ...
      }
      that is roughly equivalent to:
      int bpf_prog(struct pt_regs *ctx)
      {
        ...
        if (jmp_table[index])
          return (*jmp_table[index])(ctx);
        ...
      }
      The important detail that it's not a normal call, but a tail call.
      The kernel stack is precious, so this helper reuses the current
      stack frame and jumps into another BPF program without adding
      extra call frame.
      It's trivially done in interpreter and a bit trickier in JITs.
      In case of x64 JIT the bigger part of generated assembler prologue
      is common for all programs, so it is simply skipped while jumping.
      Other JITs can do similar prologue-skipping optimization or
      do stack unwind before jumping into the next program.
      
      bpf_tail_call() arguments:
      ctx - context pointer
      jmp_table - one of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
      index - index in the jump table
      
      Since all BPF programs are idenitified by file descriptor, user space
      need to populate the jmp_table with FDs of other BPF programs.
      If jmp_table[index] is empty the bpf_tail_call() doesn't jump anywhere
      and program execution continues as normal.
      
      New BPF_MAP_TYPE_PROG_ARRAY map type is introduced so that user space can
      populate this jmp_table array with FDs of other bpf programs.
      Programs can share the same jmp_table array or use multiple jmp_tables.
      
      The chain of tail calls can form unpredictable dynamic loops therefore
      tail_call_cnt is used to limit the number of calls and currently is set to 32.
      
      Use cases:
      Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
      
      ==========
      - simplify complex programs by splitting them into a sequence of small programs
      
      - dispatch routine
        For tracing and future seccomp the program may be triggered on all system
        calls, but processing of syscall arguments will be different. It's more
        efficient to implement them as:
        int syscall_entry(struct seccomp_data *ctx)
        {
           bpf_tail_call(ctx, &syscall_jmp_table, ctx->nr /* syscall number */);
           ... default: process unknown syscall ...
        }
        int sys_write_event(struct seccomp_data *ctx) {...}
        int sys_read_event(struct seccomp_data *ctx) {...}
        syscall_jmp_table[__NR_write] = sys_write_event;
        syscall_jmp_table[__NR_read] = sys_read_event;
      
        For networking the program may call into different parsers depending on
        packet format, like:
        int packet_parser(struct __sk_buff *skb)
        {
           ... parse L2, L3 here ...
           __u8 ipproto = load_byte(skb, ... offsetof(struct iphdr, protocol));
           bpf_tail_call(skb, &ipproto_jmp_table, ipproto);
           ... default: process unknown protocol ...
        }
        int parse_tcp(struct __sk_buff *skb) {...}
        int parse_udp(struct __sk_buff *skb) {...}
        ipproto_jmp_table[IPPROTO_TCP] = parse_tcp;
        ipproto_jmp_table[IPPROTO_UDP] = parse_udp;
      
      - for TC use case, bpf_tail_call() allows to implement reclassify-like logic
      
      - bpf_map_update_elem/delete calls into BPF_MAP_TYPE_PROG_ARRAY jump table
        are atomic, so user space can build chains of BPF programs on the fly
      
      Implementation details:
      =======================
      - high performance of bpf_tail_call() is the goal.
        It could have been implemented without JIT changes as a wrapper on top of
        BPF_PROG_RUN() macro, but with two downsides:
        . all programs would have to pay performance penalty for this feature and
          tail call itself would be slower, since mandatory stack unwind, return,
          stack allocate would be done for every tailcall.
        . tailcall would be limited to programs running preempt_disabled, since
          generic 'void *ctx' doesn't have room for 'tail_call_cnt' and it would
          need to be either global per_cpu variable accessed by helper and by wrapper
          or global variable protected by locks.
      
        In this implementation x64 JIT bypasses stack unwind and jumps into the
        callee program after prologue.
      
      - bpf_prog_array_compatible() ensures that prog_type of callee and caller
        are the same and JITed/non-JITed flag is the same, since calling JITed
        program from non-JITed is invalid, since stack frames are different.
        Similarly calling kprobe type program from socket type program is invalid.
      
      - jump table is implemented as BPF_MAP_TYPE_PROG_ARRAY to reuse 'map'
        abstraction, its user space API and all of verifier logic.
        It's in the existing arraymap.c file, since several functions are
        shared with regular array map.
      Signed-off-by: NAlexei Starovoitov <ast@plumgrid.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      04fd61ab
  11. 02 3月, 2015 1 次提交
  12. 20 11月, 2014 1 次提交
  13. 19 11月, 2014 1 次提交
    • A
      bpf: add array type of eBPF maps · 28fbcfa0
      Alexei Starovoitov 提交于
      add new map type BPF_MAP_TYPE_ARRAY and its implementation
      
      - optimized for fastest possible lookup()
        . in the future verifier/JIT may recognize lookup() with constant key
          and optimize it into constant pointer. Can optimize non-constant
          key into direct pointer arithmetic as well, since pointers and
          value_size are constant for the life of the eBPF program.
          In other words array_map_lookup_elem() may be 'inlined' by verifier/JIT
          while preserving concurrent access to this map from user space
      
      - two main use cases for array type:
        . 'global' eBPF variables: array of 1 element with key=0 and value is a
          collection of 'global' variables which programs can use to keep the state
          between events
        . aggregation of tracing events into fixed set of buckets
      
      - all array elements pre-allocated and zero initialized at init time
      
      - key as an index in array and can only be 4 byte
      
      - map_delete_elem() returns EINVAL, since elements cannot be deleted
      
      - map_update_elem() replaces elements in an non-atomic way
        (for atomic updates hashtable type should be used instead)
      Signed-off-by: NAlexei Starovoitov <ast@plumgrid.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      28fbcfa0