kernel: generic: netfilter: nft_set_hash: unaligned atomic read on struct nft_set_ext

Fix kernel panic on some 64 bit architectures.

This patch is pending upstream.
https://patchwork.ozlabs.org/project/netfilter-devel/patch/[email protected]/

Fixes: https://github.com/openwrt/openwrt/issues/17336
Link: https://github.com/openwrt/openwrt/pull/17340
Signed-off-by: Hauke Mehrtens <[email protected]>
(cherry picked from commit 4585d5abd9b77fa9ef794407c5dedcbc4001c869)

target/linux/generic/pending-6.6/605-netfilter-nft_set_hash-unaligned-atomic-read-on-stru.patch

@@ -0,0 +1,87 @@
+From 113fb8a8d1f27156f58b27ce0fc02af9b3705bf7 Mon Sep 17 00:00:00 2001
+From: Pablo Neira Ayuso <[email protected]>
+Date: Sun, 22 Dec 2024 11:02:39 +0100
+Subject: [PATCH] netfilter: nft_set_hash: unaligned atomic read on struct
+ nft_set_ext
+
+Access to genmask field in struct nft_set_ext results in unaligned
+atomic read:
+
+[   72.130109] Unable to handle kernel paging request at virtual address ffff0000c2bb708c
+[   72.131036] Mem abort info:
+[   72.131213]   ESR = 0x0000000096000021
+[   72.131446]   EC = 0x25: DABT (current EL), IL = 32 bits
+[   72.132209]   SET = 0, FnV = 0
+[   72.133216]   EA = 0, S1PTW = 0
+[   72.134080]   FSC = 0x21: alignment fault
+[   72.135593] Data abort info:
+[   72.137194]   ISV = 0, ISS = 0x00000021, ISS2 = 0x00000000
+[   72.142351]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
+[   72.145989]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
+[   72.150115] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000237d27000
+[   72.154893] [ffff0000c2bb708c] pgd=0000000000000000, p4d=180000023ffff403, pud=180000023f84b403, pmd=180000023f835403,
++pte=0068000102bb7707
+[   72.163021] Internal error: Oops: 0000000096000021 [#1] SMP
+[...]
+[   72.170041] CPU: 7 UID: 0 PID: 54 Comm: kworker/7:0 Tainted: G            E      6.13.0-rc3+ #2
+[   72.170509] Tainted: [E]=UNSIGNED_MODULE
+[   72.170720] Hardware name: QEMU QEMU Virtual Machine, BIOS edk2-stable202302-for-qemu 03/01/2023
+[   72.171192] Workqueue: events_power_efficient nft_rhash_gc [nf_tables]
+[   72.171552] pstate: 21400005 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
+[   72.171915] pc : nft_rhash_gc+0x200/0x2d8 [nf_tables]
+[   72.172166] lr : nft_rhash_gc+0x128/0x2d8 [nf_tables]
+[   72.172546] sp : ffff800081f2bce0
+[   72.172724] x29: ffff800081f2bd40 x28: ffff0000c2bb708c x27: 0000000000000038
+[   72.173078] x26: ffff0000c6780ef0 x25: ffff0000c643df00 x24: ffff0000c6778f78
+[   72.173431] x23: 000000000000001a x22: ffff0000c4b1f000 x21: ffff0000c6780f78
+[   72.173782] x20: ffff0000c2bb70dc x19: ffff0000c2bb7080 x18: 0000000000000000
+[   72.174135] x17: ffff0000c0a4e1c0 x16: 0000000000003000 x15: 0000ac26d173b978
+[   72.174485] x14: ffffffffffffffff x13: 0000000000000030 x12: ffff0000c6780ef0
+[   72.174841] x11: 0000000000000000 x10: ffff800081f2bcf8 x9 : ffff0000c3000000
+[   72.175193] x8 : 00000000000004be x7 : 0000000000000000 x6 : 0000000000000000
+[   72.175544] x5 : 0000000000000040 x4 : ffff0000c3000010 x3 : 0000000000000000
+[   72.175871] x2 : 0000000000003a98 x1 : ffff0000c2bb708c x0 : 0000000000000004
+[   72.176207] Call trace:
+[   72.176316]  nft_rhash_gc+0x200/0x2d8 [nf_tables] (P)
+[   72.176653]  process_one_work+0x178/0x3d0
+[   72.176831]  worker_thread+0x200/0x3f0
+[   72.176995]  kthread+0xe8/0xf8
+[   72.177130]  ret_from_fork+0x10/0x20
+[   72.177289] Code: 54fff984 d503201f d2800080 91003261 (f820303f)
+[   72.177557] ---[ end trace 0000000000000000 ]---
+
+Align struct nft_set_ext to word size to address this and
+documentation it.
+
+pahole reports that this increases the size of elements for rhash and
+pipapo in 8 bytes on x86_64.
+
+Fixes: 7ffc7481153b ("netfilter: nft_set_hash: skip duplicated elements pending gc run")
+Signed-off-by: Pablo Neira Ayuso <[email protected]>
+---
+ include/net/netfilter/nf_tables.h | 7 +++++--
+ 1 file changed, 5 insertions(+), 2 deletions(-)
+
+--- a/include/net/netfilter/nf_tables.h
++++ b/include/net/netfilter/nf_tables.h
+@@ -721,15 +721,18 @@ struct nft_set_ext_tmpl {
+ /**
+  *	struct nft_set_ext - set extensions
+  *
+- *	@genmask: generation mask
++ *	@genmask: generation mask, but also flags (see NFT_SET_ELEM_DEAD_BIT)
+  *	@offset: offsets of individual extension types
+  *	@data: beginning of extension data
++ *
++ *	This structure must be aligned to word size, otherwise atomic bitops
++ *	on genmask field can cause aligment failure on some archs.
+  */
+ struct nft_set_ext {
+ 	u8	genmask;
+ 	u8	offset[NFT_SET_EXT_NUM];
+ 	char	data[];
+-};
++} __aligned(BITS_PER_LONG / 8);
+ 
+ static inline void nft_set_ext_prepare(struct nft_set_ext_tmpl *tmpl)
+ {