FAILED: patch "[PATCH] riscv: patch: fix handling of bpf-jit execmem addresses" failed to apply to 6.18-stable tree

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 <[email protected]>.

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 '<[email protected]>' --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 <[email protected]>
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().

index 2239c28981bc..2b5adf01c550 100644
@@ -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);

From: Vivian Wang <[email protected]>

[ Upstream commit 6b60a128c2f43180664a614830f3c529497e0394 ]

Similarly to commit 8d09e2d569f6 ("arm64: patching: avoid early page_to_phys()"), avoid using phys_to_page() for the kernel address case in patch_map().

Since this is called from apply_boot_alternatives() in setup_arch(), and commit 4267739cabb8 ("arch, mm: consolidate initialization of SPARSE memory model") has moved sparse_init() to after setup_arch(), phys_to_page() is not available there yet, and it panics on boot with SPARSEMEM on RV32, which does not use SPARSEMEM_VMEMMAP.

Stable-dep-of: a510e1ae8c90 ("riscv: patch: fix handling of bpf-jit execmem addresses")

---
 arch/riscv/kernel/patch.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

index db13c9ddf9e3d..16b243376f362 100644
@@ -42,19 +42,20 @@ static inline bool is_kernel_exittext(uintptr_t addr)
 static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
 {
 	uintptr_t uintaddr = (uintptr_t) addr;
-	struct page *page;
+	phys_addr_t phys;
 
-	if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr))
-		page = phys_to_page(__pa_symbol(addr));
-	else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
-		page = vmalloc_to_page(addr);
-	else
-		return addr;
+	if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) {
+		phys = __pa_symbol(addr);
+	} else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) {
+		struct page *page = vmalloc_to_page(addr);
 
-	BUG_ON(!page);
+		BUG_ON(!page);
+		phys = page_to_phys(page) + offset_in_page(addr);
+	} else {
+		return addr;
+	}
 
-	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
-					 offset_in_page(addr));
+	return (void *)set_fixmap_offset(fixmap, phys);
 }
 
 static void patch_unmap(int fixmap)

2.53.0

From: Wei-Jie Hung <[email protected]>

[ Upstream commit a510e1ae8c9030750c2edf7b0bc9b186cd8c7a06 ]

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().

---
 arch/riscv/kernel/patch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 16b243376f362..1e8f1ac5a755f 100644
@@ -46,7 +46,7 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
 
 	if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) {
 		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);

2.53.0