smc: Fix various oops due to inet_sock type confusion.

q2ven · kuba-moo · commit 60ada4fe644e · 2025-07-14T17:12:42.000-07:00
syzbot reported weird splats [0][1] in cipso_v4_sock_setattr() while freeing inet_sk(sk)->inet_opt. The address was freed multiple times even though it was read-only memory. cipso_v4_sock_setattr() did nothing wrong, and the root cause was type confusion. The cited commit made it possible to create smc_sock as an INET socket. The issue is that struct smc_sock does not have struct inet_sock as the first member but hijacks AF_INET and AF_INET6 sk_family, which confuses various places. In this case, inet_sock.inet_opt was actually smc_sock.clcsk_data_ready(), which is an address of a function in the text segment. $ pahole -C inet_sock vmlinux struct inet_sock { ... struct ip_options_rcu * inet_opt; /* 784 8 */ $ pahole -C smc_sock vmlinux struct smc_sock { ... void (*clcsk_data_ready)(struct sock *); /* 784 8 */ The same issue for another field was reported before. [2][3] At that time, an ugly hack was suggested [4], but it makes both INET and SMC code error-prone and hard to change. Also, yet another variant was fixed by a hacky commit 98d4435 ("net/smc: prevent NULL pointer dereference in txopt_get"). Instead of papering over the root cause by such hacks, we should not allow non-INET socket to reuse the INET infra. Let's add inet_sock as the first member of smc_sock. [0]: kvfree_call_rcu(): Double-freed call. rcu_head 000000006921da73 WARNING: CPU: 0 PID: 6718 at mm/slab_common.c:1956 kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 Modules linked in: CPU: 0 UID: 0 PID: 6718 Comm: syz.0.17 Tainted: G W 6.16.0-rc4-syzkaller-g7482bb149b9f #0 PREEMPT Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 lr : kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 sp : ffff8000a03a7730 x29: ffff8000a03a7730 x28: 00000000fffffff5 x27: 1fffe000184823d3 x26: dfff800000000000 x25: ffff0000c2411e9e x24: ffff0000dd88da00 x23: ffff8000891ac9a0 x22: 00000000ffffffea x21: ffff8000891ac9a0 x20: ffff8000891ac9a0 x19: ffff80008afc2480 x18: 00000000ffffffff x17: 0000000000000000 x16: ffff80008ae642c8 x15: ffff700011ede14c x14: 1ffff00011ede14c x13: 0000000000000004 x12: ffffffffffffffff x11: ffff700011ede14c x10: 0000000000ff0100 x9 : 5fa3c1ffaf0ff000 x8 : 5fa3c1ffaf0ff000 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff8000a03a7078 x4 : ffff80008f766c20 x3 : ffff80008054d360 x2 : 0000000000000000 x1 : 0000000000000201 x0 : 0000000000000000 Call trace: kvfree_call_rcu+0x94/0x3f0 mm/slab_common.c:1955 (P) cipso_v4_sock_setattr+0x2f0/0x3f4 net/ipv4/cipso_ipv4.c:1914 netlbl_sock_setattr+0x240/0x334 net/netlabel/netlabel_kapi.c:1000 smack_netlbl_add+0xa8/0x158 security/smack/smack_lsm.c:2581 smack_inode_setsecurity+0x378/0x430 security/smack/smack_lsm.c:2912 security_inode_setsecurity+0x118/0x3c0 security/security.c:2706 __vfs_setxattr_noperm+0x174/0x5c4 fs/xattr.c:251 __vfs_setxattr_locked+0x1ec/0x218 fs/xattr.c:295 vfs_setxattr+0x158/0x2ac fs/xattr.c:321 do_setxattr fs/xattr.c:636 [inline] file_setxattr+0x1b8/0x294 fs/xattr.c:646 path_setxattrat+0x2ac/0x320 fs/xattr.c:711 __do_sys_fsetxattr fs/xattr.c:761 [inline] __se_sys_fsetxattr fs/xattr.c:758 [inline] __arm64_sys_fsetxattr+0xc0/0xdc fs/xattr.c:758 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 [1]: Unable to handle kernel write to read-only memory at virtual address ffff8000891ac9a8 KASAN: probably user-memory-access in range [0x0000000448d64d40-0x0000000448d64d47] Mem abort info: ESR = 0x000000009600004e EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x0e: level 2 permission fault Data abort info: ISV = 0, ISS = 0x0000004e, ISS2 = 0x00000000 CM = 0, WnR = 1, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000207144000 [ffff8000891ac9a8] pgd=0000000000000000, p4d=100000020f950003, pud=100000020f951003, pmd=0040000201000781 Internal error: Oops: 000000009600004e [#1] SMP Modules linked in: CPU: 0 UID: 0 PID: 6946 Comm: syz.0.69 Not tainted 6.16.0-rc4-syzkaller-g7482bb149b9f #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : kvfree_call_rcu+0x31c/0x3f0 mm/slab_common.c:1971 lr : add_ptr_to_bulk_krc_lock mm/slab_common.c:1838 [inline] lr : kvfree_call_rcu+0xfc/0x3f0 mm/slab_common.c:1963 sp : ffff8000a28a7730 x29: ffff8000a28a7730 x28: 00000000fffffff5 x27: 1fffe00018b09bb3 x26: 0000000000000001 x25: ffff80008f66e000 x24: ffff00019beaf498 x23: ffff00019beaf4c0 x22: 0000000000000000 x21: ffff8000891ac9a0 x20: ffff8000891ac9a0 x19: 0000000000000000 x18: 00000000ffffffff x17: ffff800093363000 x16: ffff80008052c6e4 x15: ffff700014514ecc x14: 1ffff00014514ecc x13: 0000000000000004 x12: ffffffffffffffff x11: ffff700014514ecc x10: 0000000000000001 x9 : 0000000000000001 x8 : ffff00019beaf7b4 x7 : ffff800080a94154 x6 : 0000000000000000 x5 : ffff8000935efa60 x4 : 0000000000000008 x3 : ffff80008052c7fc x2 : 0000000000000001 x1 : ffff8000891ac9a0 x0 : 0000000000000001 Call trace: kvfree_call_rcu+0x31c/0x3f0 mm/slab_common.c:1967 (P) cipso_v4_sock_setattr+0x2f0/0x3f4 net/ipv4/cipso_ipv4.c:1914 netlbl_sock_setattr+0x240/0x334 net/netlabel/netlabel_kapi.c:1000 smack_netlbl_add+0xa8/0x158 security/smack/smack_lsm.c:2581 smack_inode_setsecurity+0x378/0x430 security/smack/smack_lsm.c:2912 security_inode_setsecurity+0x118/0x3c0 security/security.c:2706 __vfs_setxattr_noperm+0x174/0x5c4 fs/xattr.c:251 __vfs_setxattr_locked+0x1ec/0x218 fs/xattr.c:295 vfs_setxattr+0x158/0x2ac fs/xattr.c:321 do_setxattr fs/xattr.c:636 [inline] file_setxattr+0x1b8/0x294 fs/xattr.c:646 path_setxattrat+0x2ac/0x320 fs/xattr.c:711 __do_sys_fsetxattr fs/xattr.c:761 [inline] __se_sys_fsetxattr fs/xattr.c:758 [inline] __arm64_sys_fsetxattr+0xc0/0xdc fs/xattr.c:758 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x180 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 Code: aa1f03e2 52800023 97ee1e8d b4000195 (f90006b4) Fixes: d25a92c ("net/smc: Introduce IPPROTO_SMC") Reported-by: syzbot+40bf00346c3fe40f90f2@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/686d9b50.050a0220.1ffab7.0020.GAE@google.com/ Tested-by: syzbot+40bf00346c3fe40f90f2@syzkaller.appspotmail.com Reported-by: syzbot+f22031fad6cbe52c70e7@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/686da0f3.050a0220.1ffab7.0022.GAE@google.com/ Reported-by: syzbot+271fed3ed6f24600c364@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=271fed3ed6f24600c364 # [2] Link: https://lore.kernel.org/netdev/99f284be-bf1d-4bc4-a629-77b268522fff@huawei.com/ # [3] Link: https://lore.kernel.org/netdev/20250331081003.1503211-1-wangliang74@huawei.com/ # [4] Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com> Reviewed-by: D. Wythe <alibuda@linux.alibaba.com> Reviewed-by: Wang Liang <wangliang74@huawei.com> Link: https://patch.msgid.link/20250711060808.2977529-1-kuniyu@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
@@ -30,6 +30,10 @@
 #include <linux/splice.h>
 
 #include <net/sock.h>
+#include <net/inet_common.h>
+#if IS_ENABLED(CONFIG_IPV6)
+#include <net/ipv6.h>
+#endif
 #include <net/tcp.h>
 #include <net/smc.h>
 #include <asm/ioctls.h>
@@ -360,6 +364,16 @@ static void smc_destruct(struct sock *sk)
 		return;
 	if (!sock_flag(sk, SOCK_DEAD))
 		return;
+	switch (sk->sk_family) {
+	case AF_INET:
+		inet_sock_destruct(sk);
+		break;
+#if IS_ENABLED(CONFIG_IPV6)
+	case AF_INET6:
+		inet6_sock_destruct(sk);
+		break;
+#endif
+	}
 }
 
 static struct lock_class_key smc_key;
diff --git a/net/smc/smc.h b/net/smc/smc.h
@@ -283,10 +283,10 @@ struct smc_connection {
 };
 
 struct smc_sock {				/* smc sock container */
-	struct sock		sk;
-#if IS_ENABLED(CONFIG_IPV6)
-	struct ipv6_pinfo	*pinet6;
-#endif
+	union {
+		struct sock		sk;
+		struct inet_sock	icsk_inet;
+	};
 	struct socket		*clcsock;	/* internal tcp socket */
 	void			(*clcsk_state_change)(struct sock *sk);
 						/* original stat_change fct. */
