blktrace: always record ftrace events as blk_io_trace2 - #166
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The ftrace ring buffer always uses the v2 (blk_io_trace2) format, but __blk_add_trace() switched the reserve size and record format on bt->version. That field only describes the relay/classic blktrace record format and must not change what goes into the ftrace buffer: the ftrace readers (print_one_line() and friends) unconditionally parse blk_io_trace2. The BLKTRACESETUP ioctl sets bt->version to 1. With the blk tracer also enabled, __blk_add_trace() recorded a 48-byte v1 event into the ftrace ring buffer, but the reader parses the 64-byte v2 layout, so pdu_start() points 16 bytes past the PDU and blk_log_remap() reads out of bounds - a use-after-free when the ring buffer page is resized concurrently. Always use the v2 format in the blk_tracer path, and initialize bt->version to 2 in blk_trace_setup_queue() so the sysfs-enabled path no longer leaves it uninitialized. Fixes: e48886b ("blktrace: for ftrace use correct trace format ver") Reported-by: syzbot+4dfd96209d744263a972@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=4dfd96209d744263a972 Tested-by: syzbot+4dfd96209d744263a972@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Adriano Cordova <adrianox@gmail.com>
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Pull request for series with
subject: blktrace: always record ftrace events as blk_io_trace2
version: 1
url: http://redsun45:8000/project/linux-block/list/?series=792