Subject: FAILED: patch "[PATCH] riscv: patch: fix handling of bpf-jit execmem addresses" failed to apply to 6.18-stable tree
To: imbigking12@gmail.com,pjw@kernel.org,pulehui@huawei.com
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Mon, 12 Oct 2026 17:24:08 +0200
Message-ID: <2026101208-patio-blinking-92df@gregkh>
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The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x a510e1ae8c9030750c2edf7b0bc9b186cd8c7a06
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026101208-patio-blinking-92df@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a510e1ae8c9030750c2edf7b0bc9b186cd8c7a06 Mon Sep 17 00:00:00 2001
From: Wei-Jie Hung <imbigking12@gmail.com>
Date: Mon, 5 Oct 2026 19:02:38 -0600
Subject: [PATCH] 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().

Fixes: 2c9e5d4a0082 ("bpf: remove CONFIG_BPF_JIT dependency on CONFIG_MODULES of")
Signed-off-by: Wei-Jie Hung <imbigking12@gmail.com>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Pu Lehui <pulehui@huawei.com>
Link: https://patch.msgid.link/20260914115607.350097-1-imbigking12@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Paul Walmsley <pjw@kernel.org>

diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 2239c28981bc..2b5adf01c550 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -48,7 +48,7 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
 		if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
 			return addr;
 		phys = __pa_symbol(addr);
-	} else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) {
+	} else if (IS_ENABLED(CONFIG_EXECMEM)) {
 		struct page *page = vmalloc_to_page(addr);
 
 		BUG_ON(!page);