kprobes: Skip disarmed probes when checking optkprobe overlap

Overview

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

kprobes: Skip disarmed probes when checking optkprobe overlap

On x86, an optkprobe at A replaces five bytes with a jump. If a disabled probe B is at A+2, get_optimized_kprobe() stops at B when arming a new probe C at A+4. It leaves A optimized:

          A    A+1  A+2  A+3  A+4

A's jump | e9 | d0 | d1 | d2 | d3 | after C | e9 | d0 | d1 | d2 | cc |

The INT3 for C overwrites the last byte of A's jump displacement, so execution can jump to the wrong address. B can have prepared optinsns while disarmed, but has no jump to unoptimize.

Continue past disarmed and unprepared probes to find the active optimized probe before arming a probe in its jump.

Affected

• Linux >= afd66255b9a48f5851326ddae50e2203fbf71dc9 < 985a568171e7bdba6dcde3420d0e5bb515813457
• Linux >= afd66255b9a48f5851326ddae50e2203fbf71dc9 < 6745fa65f4115045431c0c15610e876855a04625
• Linux >= afd66255b9a48f5851326ddae50e2203fbf71dc9 < 526fac219e8b7d3369b43026bd0a1df51b811cd4
• Linux >= afd66255b9a48f5851326ddae50e2203fbf71dc9 < 7a39c732a22ec4a369af9e19fbe3d666ec83eec4
• Linux 2.6.34

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.