CVE-2026-98042

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

bpf: Don't resurrect a scalar id dropped by collect linked regs()

check cond jmp op() copies the compared registers into env->{false,true} reg{1,2} before collect linked regs() runs and copies those snapshots back into both branch states afterwards.

collect linked regs() records at most LINKED REGS MAX members of a linked registers group in the jump history and calls clear scalar id() for every member that does not fit. The compared register is not exempt from that.

As a consequence, sync linked regs() might adjust ranges for more registers than bpf bt sync linked regs() can propagate precision to.

Collect the linked registers before the snapshots are taken instead. This might lead to some unnecessary clear scalar id's, but from previous testing situations with many linked registers are extremely rare.