CVE-2026-99092
Received
Received - Intake
Kernel text patching flaw in Linux RISC-V
Vulnerability report for CVE-2026-99092, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-26
Last updated on: 2026-10-26
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
riscv: patch: fix handling of bpf-jit execmem addresses
Commit 8718e5a3090b ("riscv: patch: skip fixmap mapping when kernel text
is already writable") gated the core_kernel_text() branch of patch_map()
on CONFIG_STRICT_KERNEL_RWX, and explicitly left the vmalloc branch
unchanged. That branch has a separate problem.
That branch only creates a temporary writable fixmap alias when
CONFIG_STRICT_MODULE_RWX is enabled, and otherwise assumes the target is
directly writable and returns the address unchanged. That assumption no
longer holds: bpf_prog_pack_alloc calls set_memory_rox() on every pack
unconditionally in alloc_new_pack(), independently of any
CONFIG_STRICT_*_RWX option, so BPF text in the vmalloc area is read-only
regardless of what CONFIG_STRICT_MODULE_RWX says.
With CONFIG_STRICT_MODULE_RWX=n, patch_map() returns the read-only
address directly, the subsequent copy_to_kernel_nofault() takes a
page fault and returns -EFAULT. bpf_arch_text_copy() turns that into
-EINVAL, which propagates through bpf_jit_binary_pack_finalize() to the
WARN_ON() in bpf_int_jit_compile() and leaves the program un-JITed.
Note that BPF cannot be fixed the way kprobes was in
commit bdc46e507b59 ("riscv: mm: make EXECMEM_KPROBES writable without
CONFIG_STRICT_MODULE_RWX"). EXECMEM_BPF is already PAGE_KERNEL, i.e.
writable at allocation time; the read-only mapping is established
afterwards by generic code in alloc_new_pack(), which arch code cannot
influence. The only place this can be handled is patch_map().
This is the same problem that was fixed on arm64 by commit b1480ed230ac
("arm64: patching: fix handling of execmem addresses"), and the fix is
the same: CONFIG_EXECMEM is what actually tracks whether the vmalloc
area can hold executable memory that needs a temporary alias to be
written. CONFIG_BPF_JIT, CONFIG_KPROBES and CONFIG_MODULES all select
it.
Note that this is not limited to CONFIG_MODULES=n. Unlike arm64, riscv
selects CONFIG_ARCH_OPTIONAL_KERNEL_RWX, so CONFIG_STRICT_MODULE_RWX can
be disabled with CONFIG_MODULES=y as well, and the bug is reachable in
that configuration too.
The !CONFIG_MMU build is unaffected: it has its own __patch_insn_set()
and __patch_insn_write() implementations and never calls patch_map().
CVSS Scores
EPSS Scores
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Meta Information
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
