CVE-2026-98540fprobe: Terminate the fgraph_data list when the reservation is not filled

Official description

In the Linux kernel, the following vulnerability has been resolved: fprobe: Terminate the fgraph_data list when the reservation is not filled fprobe_fgraph_entry() reserves shadow stack space for every fprobe with an exit handler, but only fills it for those whose entry handler returns 0. fgraph_reserve_data() does not clear the area, so fprobe_return() parses the unused tail as headers left over from an earlier call, and an exit handler can run twice or despite its entry handler asking to skip it. Write a zero word after the last entry to terminate the walk. A zeroed slot does not decode to a NULL fprobe on the arches that encode the header into one unsigned long, since arch_decode_fprobe_header_fp() ORs in FPROBE_HEADER_MSB_PATTERN, so make read_fprobe_header() return NULL for a zeroed slot.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b7459fddcb27a4b7d01067678172afa362cf660d
• https://git.kernel.org/stable/c/1d653a183973f5283a3db5a38cd5e195eb152244