Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:EOL][EOL]dm: fix unconditional IO throttle caused by REQ_PREFLUSH[EOL][EOL]When a bio with REQ_PREFLUSH is submitted to dm, __send_empty_flush()[EOL]generates a flush_bio with REQ_OP_WRITE  ( REQ_PREFLUSH | REQ_SYNC,[EOL)which causes the flush_bio to be throttled by wbt_wait().EOL][EOL]An example from v5.4, similar problem also exists in upstream:[EOL][EOL]    crash> bt 2091206[EOL]    PID: 2091206  TASK: ffff2050df92a300  CPU: 109  COMMAND: "kworker/u260:0"[EOL]     #0 [ffff800084a2f7f0] __switch_to at ffff80004008aeb8[EOL]     #1 [ffff800084a2f820] __schedule at ffff800040bfa0c4[EOL]     #2 [ffff800084a2f880] schedule at ffff800040bfa4b4[EOL]     #3 [ffff800084a2f8a0] io_schedule at ffff800040bfa9c4[EOL]     #4 [ffff800084a2f8c0] rq_qos_wait at ffff8000405925bc[EOL]     #5 [ffff800084a2f940] wbt_wait at ffff8000405bb3a0[EOL]     #6 [ffff800084a2f9a0] __rq_qos_throttle at ffff800040592254[EOL]     #7 [ffff800084a2f9c0] blk_mq_make_request at ffff80004057cf38[EOL]     #8 [ffff800084a2fa60] generic_make_request at ffff800040570138[EOL]     #9 [ffff800084a2fae0] submit_bio at ffff8000405703b4[EOL]    #10 [ffff800084a2fb50] xlog_write_iclog at ffff800001280834 [xfs][EOL]    #11 [ffff800084a2fbb0] xlog_sync at ffff800001280c3c [xfs][EOL]    #12 [ffff800084a2fbf0] xlog_state_release_iclog at ffff800001280df4 [xfs][EOL]    #13 [ffff800084a2fc10] xlog_write at ffff80000128203c [xfs][EOL]    #14 [ffff800084a2fcd0] xlog_cil_push at ffff8000012846dc [xfs][EOL]    #15 [ffff800084a2fda0] xlog_cil_push_work at ffff800001284a2c [xfs][EOL]    #16 [ffff800084a2fdb0] process_one_work at ffff800040111d08[EOL]    #17 [ffff800084a2fe00] worker_thread at ffff8000401121cc[EOL]    #18 [ffff800084a2fe70] kthread at ffff800040118de4[EOL][EOL]After commit 2def2845cc33 ("xfs: don't allow log IO to be throttled"),[EOL]the metadata submitted by xlog_write_iclog() should not be throttled.[EOL]But due to the existence of the dm layer, throttling flush_bio indirectly[EOL]causes the metadata bio to be throttled.[EOL][EOL]Fix this by conditionally adding REQ_IDLE to flush_bio.bi_opf, which makes[EOL]wbt_should_throttle() return false to avoid wbt_wait().

CREATE(Triage):(User=lchen-cn) [CVE-2025-38063 (https://nvd.nist.gov/vuln/detail/CVE-2025-38063)