In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
bpf, s390: Clear fetch destination on faulting arena atomic<\/p>\n
Same missing register clear as on riscv64. A RMW atomic on an arena pointer
\nis converted to BPF_PROBE_ATOMIC and gets an exception table entry, but
\nbpf_jit_probe_atomic_pre() only fills in the arena base and the probe
\noffset, leaving probe->reg at the -1 that bpf_jit_probe_init() set, which
\nbpf_jit_probe_post() writes into the entry and ex_handler_bpf() then reads
\nback as “there is nothing to clear”.<\/p>\n
That is right for a plain BPF_{ADD,AND,OR,XOR}, which only writes memory,
\nbut an RMW carrying BPF_FETCH also reads the old value into a register:
\nsrc_reg for BPF_{ADD,AND,OR,XOR} | BPF_FETCH and BPF_XCHG, and r0 for
\nBPF_CMPXCHG. So on a fault over an unmapped arena page the program resumes
\nat the landing pad with whatever that register held before the atomic
\ninstead of the 0 that every other BPF_PROBE_* access delivers.<\/p>\n
Fill probe->reg in from bpf_atomic_load_reg(). Unlike x86-64 and arm64,
\ns390x does not report arena violations from its exception handler, so there
\nis no access direction to correct here, only the missing register clear.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
bpf, s390: Clear fetch destination on faulting arena atomic<\/p>\n
Same missing register clear as on riscv64. A RMW atomic on an arena po<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-25620","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/25620","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=25620"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25620"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25620"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}