coresight: etm4x: fix underflow for usage of (nrseqstate - 1)

Summary

In the Linux kernel, the following vulnerability has been resolved: coresight: etm4x: fix underflow for usage of (nrseqstate - 1) According to IHI006H Embedded Trace Macrocell Architecture Specification[0], TRCSEQEVR<n> is implemented only when TRCIDR5.NUMSEQSTATE is 0b100, in which case n ranges from 0 to 2; otherwise, TRCIDR5.NUMSEQSTATE is 0b000. IOW, the number of usage in the initialisation or setting TRCSEQEVR<n> with drvdata->nrseqstate - 1 in the loop could make underflow issue when TRCIDR5.NUMSEQSTATE is 0b000. Therefore, introduce nr_seq_ctrls field and untie it from nrseqstate. As part of this introduce ETM_MAX_SEQ_TRANSITIONS macro and apply nr_seq_ctrls and above macro to TRCSEQEVR<n> relevant fields setup.

Timeline

1. Sep 17, 2026, 4:08 PM UTCCVE published
2. Oct 19, 2026, 9:00 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in 8d669db59f7283b838e029af29da12e505265fae; From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in 4091f2d5b26d117c992ffcce1a5df425a0daedcd; From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in be7b2de5b9a96ae68ffa3528e0a40d63e0fd8148; From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in 4f9a0f548413bf864f609c9f4bc56e3f1b3577d4; From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in 1ade9a335c69fc735cb7b3f222ed35ab135540fb; From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in 5ac900f73ce1d4d8308f40752b51bc8a02b244d2; From 2e1cdfe184b5202d51e0611d7a051e2bea303946 · fixed in 1674d9bff8073bdee5dbc200f56fc3caa28d0566

• Linux Linux

  4.2

• KernelLinux

  From 4.2.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 7