This is a note to let you know that I've just added the patch titled
bpf: Fix softlockup in arena_map_free on 64k page kernel
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-fix-softlockup-in-arena_map_free-on-64k-page-ker.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f4ceb8e8a08211d696ca281af4e531074160ef4e
Author: Alan Maguire <alan.maguire@xxxxxxxxxx>
Date: Wed Feb 5 17:00:59 2025 +0000
bpf: Fix softlockup in arena_map_free on 64k page kernel
[ Upstream commit 517e8a7835e8cfb398a0aeb0133de50e31cae32b ]
On an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y,
arena_htab tests cause a segmentation fault and soft lockup.
The same failure is not observed with 4k pages on aarch64.
It turns out arena_map_free() is calling
apply_to_existing_page_range() with the address returned by
bpf_arena_get_kern_vm_start(). If this address is not page-aligned
the code ends up calling apply_to_pte_range() with that unaligned
address causing soft lockup.
Fix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the
division by 2 in bpf_arena_get_kern_vm_start() returns
a page-aligned value.
Fixes: 317460317a02 ("bpf: Introduce bpf_arena.")
Reported-by: Colm Harrington <colm.harrington@xxxxxxxxxx>
Suggested-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250205170059.427458-1-alan.maguire@xxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
index 8caf56a308d96..eac5d1edefe97 100644
--- a/kernel/bpf/arena.c
+++ b/kernel/bpf/arena.c
@@ -39,7 +39,7 @@
*/
/* number of bytes addressable by LDX/STX insn with 16-bit 'off' field */
-#define GUARD_SZ (1ull << sizeof_field(struct bpf_insn, off) * 8)
+#define GUARD_SZ round_up(1ull << sizeof_field(struct bpf_insn, off) * 8, PAGE_SIZE << 1)
#define KERN_VM_SZ (SZ_4G + GUARD_SZ)
struct bpf_arena {
