coresight: tmc-etr: Fix race condition between sysfs and perf mode

Summary

In the Linux kernel, the following vulnerability has been resolved: coresight: tmc-etr: Fix race condition between sysfs and perf mode When trying to run perf and sysfs mode simultaneously, the WARN_ON() in tmc_etr_enable_hw() is triggered sometimes: WARNING: CPU: 42 PID: 3911571 at drivers/hwtracing/coresight/coresight-tmc-etr.c:1060 tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] [..snip..] Call trace: tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] (P) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] (L) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] coresight_enable_path+0x1c8/0x218 [coresight] coresight_enable_sysfs+0xa4/0x228 [coresight] enable_source_store+0x58/0xa8 [coresight] dev_attr_store+0x20/0x40 sysfs_kf_write+0x4c/0x68 kernfs_fop_write_iter+0x120/0x1b8 vfs_write+0x2c8/0x388 ksys_write+0x74/0x108 __arm64_sys_write+0x24/0x38 el0_svc_common.constprop.0+0x64/0x148 do_el0_svc+0x24/0x38 el0_svc+0x3c/0x130 el0t_64_sync_handler+0xc8/0xd0 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Since the enablement of sysfs mode is separeted into two critical regions, one for sysfs buffer allocation and another for hardware enablement, it's possible to race with the perf mode. Fix this by double check whether the perf mode's been used before enabling the hardware in sysfs mode. mode: [sysfs mode] [perf mode] tmc_etr_get_sysfs_buffer() spin_lock(&drvdata->spinlock) [sysfs buffer allocation] spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() drvdata->etr_buf = etr_perf->etr_buf spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() WARN_ON(drvdata->etr_buf) // WARN sicne etr_buf initialized at the perf side spin_unlock(&drvdata->spinlock) With this fix, we retain the check for CS_MODE_PERF in get_etr_sysfs_buf. This ensures we verify whether the perf mode's already running before we actually allocate the buffer. Then we can save the time of allocating/freeing the sysfs buffer if race with the perf mode.

Timeline

1. Jun 3, 2026, 3:50 PM UTCCVE published
2. Oct 21, 2026, 12:41 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 296b01fd106e787d4463974a7f42d286a5df08cd · fixed in 3e8cdf184646c28c5ea5fba754d24a3b29068739; From 296b01fd106e787d4463974a7f42d286a5df08cd · fixed in 206b6f672613d08b33e951a744d0a1c6ac5ad8ad; From 296b01fd106e787d4463974a7f42d286a5df08cd · fixed in 38a07194bbcddb18d77dad40ba9978d994c0b74c; From 296b01fd106e787d4463974a7f42d286a5df08cd · fixed in 6906aa70d4fc5900b954136e20e27c2be6d1acab; From 296b01fd106e787d4463974a7f42d286a5df08cd · fixed in e6e43e82c79c97917cbe356c07e8a6f3f982ab53

• Linux Linux

  6.5

• KernelLinux

  From 6.5.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.14; From 6.19.0 · fixed in 6.19.4

References 5