Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

ring-buffer: Handle race between rb_move_tail and rb_check_pages

It seems a data race between ring_buffer writing and integrity check. That is, RB_FLAG of head_page is been updating, while at same time RB_FLAG was cleared when doing integrity check rb_check_pages():

rb_check_pages() rb_handle_head_page(): -------- -------- rb_head_page_deactivate() rb_head_page_set_normal() rb_head_page_activate()

We do intergrity test of the list to check if the list is corrupted and it is still worth doing it. So, let's refactor rb_check_pages() such that we no longer clear and set flag during the list sanity checking.

[1] and [2] are the test to reproduce and the crash report respectively.

1: ``` read_trace.sh while true; do # the "trace" file is closed after read head -1 /sys/kernel/tracing/trace > /dev/null done ``` ``` repro.sh sysctl -w kernel.panic_on_warn=1 # function tracer will writing enough data into ring_buffer echo function > /sys/kernel/tracing/current_tracer ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ./read_trace.sh & ```

2: ------------[ cut here ]------------ WARNING: CPU: 9 PID: 62 at kernel/trace/ring_buffer.c:2653 rb_move_tail+0x450/0x470 Modules linked in: CPU: 9 PID: 62 Comm: ksoftirqd/9 Tainted: G W…