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  1. Jan 11, 2022
    • Naveen N. Rao's avatar
      tracing: Fix check for trace_percpu_buffer validity in get_trace_buf() · 24bb91f9
      Naveen N. Rao authored
      commit 823e670f upstream.
      
      With the new osnoise tracer, we are seeing the below splat:
          Kernel attempted to read user page (c7d880000) - exploit attempt? (uid: 0)
          BUG: Unable to handle kernel data access on read at 0xc7d880000
          Faulting instruction address: 0xc0000000002ffa10
          Oops: Kernel access of bad area, sig: 11 [#1]
          LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
          ...
          NIP [c0000000002ffa10] __trace_array_vprintk.part.0+0x70/0x2f0
          LR [c0000000002ff9fc] __trace_array_vprintk.part.0+0x5c/0x2f0
          Call Trace:
          [c0000008bdd73b80] [c0000000001c49cc] put_prev_task_fair+0x3c/0x60 (unreliable)
          [c0000008bdd73be0] [c000000000301430] trace_array_printk_buf+0x70/0x90
          [c0000008bdd73c00] [c0000000003178b0] trace_sched_switch_callback+0x250/0x290
          [c0000008bdd73c90] [c000000000e70d60] __schedule+0x410/0x710
          [c0000008bdd73d40] [c000000000e710c0] schedule+0x60/0x130
          [c0000008bdd73d70] [c000000000030614] interrupt_exit_user_prepare_main+0x264/0x270
          [c0000008bdd73de0] [c000000000030a70] syscall_exit_prepare+0x150/0x180
          [c0000008bdd73e10] [c00000000000c174] system_call_vectored_common+0xf4/0x278
      
      osnoise tracer on ppc64le is triggering osnoise_taint() for negative
      duration in get_int_safe_duration() called from
      trace_sched_switch_callback()->thread_exit().
      
      The problem though is that the check for a valid trace_percpu_buffer is
      incorrect in get_trace_buf(). The check is being done after calculating
      the pointer for the current cpu, rather than on the main percpu pointer.
      Fix the check to be against trace_percpu_buffer.
      
      Link: https://lkml.kernel.org/r/a920e4272e0b0635cf20c444707cbce1b2c8973d.1640255304.git.naveen.n.rao@linux.vnet.ibm.com
      
      
      
      Cc: stable@vger.kernel.org
      Fixes: e2ace001 ("tracing: Choose static tp_printk buffer by explicit nesting count")
      Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      24bb91f9
  2. Jan 05, 2022
  3. Dec 29, 2021