• Steven Rostedt's avatar
    tracing: Have filter check for balanced ops · 63dec311
    Steven Rostedt authored
    commit 2cf30dc180cea808077f003c5116388183e54f9e upstream.
    
    When the following filter is used it causes a warning to trigger:
    
     # cd /sys/kernel/debug/tracing
     # echo "((dev==1)blocks==2)" > events/ext4/ext4_truncate_exit/filter
    -bash: echo: write error: Invalid argument
     # cat events/ext4/ext4_truncate_exit/filter
    ((dev==1)blocks==2)
    ^
    parse_error: No error
    
     ------------[ cut here ]------------
     WARNING: CPU: 2 PID: 1223 at kernel/trace/trace_events_filter.c:1640 replace_preds+0x3c5/0x990()
     Modules linked in: bnep lockd grace bluetooth  ...
     CPU: 3 PID: 1223 Comm: bash Tainted: G        W       4.1.0-rc3-test+ #450
     Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
      0000000000000668 ffff8800c106bc98 ffffffff816ed4f9 ffff88011ead0cf0
      0000000000000000 ffff8800c106bcd8 ffffffff8107fb07 ffffffff8136b46c
      ffff8800c7d81d48 ffff8800d4c2bc00 ffff8800d4d4f920 00000000ffffffea
     Call Trace:
      [<ffffffff816ed4f9>] dump_stack+0x4c/0x6e
      [<ffffffff8107fb07>] warn_slowpath_common+0x97/0xe0
      [<ffffffff8136b46c>] ? _kstrtoull+0x2c/0x80
      [<ffffffff8107fb6a>] warn_slowpath_null+0x1a/0x20
      [<ffffffff81159065>] replace_preds+0x3c5/0x990
      [<ffffffff811596b2>] create_filter+0x82/0xb0
      [<ffffffff81159944>] apply_event_filter+0xd4/0x180
      [<ffffffff81152bbf>] event_filter_write+0x8f/0x120
      [<ffffffff811db2a8>] __vfs_write+0x28/0xe0
      [<ffffffff811dda43>] ? __sb_start_write+0x53/0xf0
      [<ffffffff812e51e0>] ? security_file_permission+0x30/0xc0
      [<ffffffff811dc408>] vfs_write+0xb8/0x1b0
      [<ffffffff811dc72f>] SyS_write+0x4f/0xb0
      [<ffffffff816f5217>] system_call_fastpath+0x12/0x6a
     ---[ end trace e11028bd95818dcd ]---
    
    Worse yet, reading the error message (the filter again) it says that
    there was no error, when there clearly was. The issue is that the
    code that checks the input does not check for balanced ops. That is,
    having an op between a closed parenthesis and the next token.
    
    This would only cause a warning, and fail out before doing any real
    harm, but it should still not caues a warning, and the error reported
    should work:
    
     # cd /sys/kernel/debug/tracing
     # echo "((dev==1)blocks==2)" > events/ext4/ext4_truncate_exit/filter
    -bash: echo: write error: Invalid argument
     # cat events/ext4/ext4_truncate_exit/filter
    ((dev==1)blocks==2)
    ^
    parse_error: Meaningless filter expression
    
    And give no kernel warning.
    
    Link: http://lkml.kernel.org/r/20150615175025.7e809215@gandalf.local.home
    
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
    Reported-by: default avatarVince Weaver <vincent.weaver@maine.edu>
    Tested-by: default avatarVince Weaver <vincent.weaver@maine.edu>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    [ luis: backported to 3.16:
      - unconditionally decrement cnt as the OP_NOT logic was introduced only
        by e12c09cf3087 ("tracing: Add NOT to filtering logic") ]
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    63dec311
trace_events_filter.c 50.5 KB