[PATCH AUTOSEL 5.4 1/2] ARM: 9434/1: cfi: Fix compilation corner case

[PATCH AUTOSEL 5.4 1/2] ARM: 9434/1: cfi: Fix compilation corner case

[Sasha Levin]

From: Linus Walleij <linus.walleij@linaro.org>

[ Upstream commit 4aea16b7cfb76bd3361858ceee6893ef5c9b5570 ]

When enabling expert mode CONFIG_EXPERT and using that power
user mode to disable the branch prediction hardening
!CONFIG_HARDEN_BRANCH_PREDICTOR, the assembly linker
in CLANG notices that some assembly in proc-v7.S does
not have corresponding C call sites, i.e. the prototypes
in proc-v7-bugs.c are enclosed in ifdef
CONFIG_HARDEN_BRANCH_PREDICTOR so this assembly:

SYM_TYPED_FUNC_START(cpu_v7_smc_switch_mm)
SYM_TYPED_FUNC_START(cpu_v7_hvc_switch_mm)

Results in:

ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_smc_switch_mm
>>> referenced by proc-v7.S:94 (.../arch/arm/mm/proc-v7.S:94)
>>> arch/arm/mm/proc-v7.o:(.text+0x108) in archive vmlinux.a

ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_hvc_switch_mm
>>> referenced by proc-v7.S:105 (.../arch/arm/mm/proc-v7.S:105)
>>> arch/arm/mm/proc-v7.o:(.text+0x124) in archive vmlinux.a

Fix this by adding an additional requirement that
CONFIG_HARDEN_BRANCH_PREDICTOR has to be enabled to compile
these assembly calls.

Closes: https://lore.kernel.org/oe-kbuild-all/202411041456.ZsoEiD7T-lkp@intel.com/

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/arm/mm/proc-v7.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 48e0ef6f0dccf..aee85fd261f5d 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -91,7 +91,7 @@ ENTRY(cpu_v7_dcache_clean_area)
 	ret	lr
 ENDPROC(cpu_v7_dcache_clean_area)
 
-#ifdef CONFIG_ARM_PSCI
+#if defined(CONFIG_ARM_PSCI) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
 	.arch_extension sec
 ENTRY(cpu_v7_smc_switch_mm)
 	stmfd	sp!, {r0 - r3}
-- 
2.43.0

[PATCH AUTOSEL 5.4 2/2] ipmr: Fix access to mfc_cache_list without lock held

[Sasha Levin]

From: Breno Leitao <leitao@debian.org>

[ Upstream commit e28acc9c1ccfcb24c08e020828f69d0a915b06ae ]

Accessing `mr_table->mfc_cache_list` is protected by an RCU lock. In the
following code flow, the RCU read lock is not held, causing the
following error when `RCU_PROVE` is not held. The same problem might
show up in the IPv6 code path.

	6.12.0-rc5-kbuilder-01145-gbac17284bdcb #33 Tainted: G            E    N
	-----------------------------
	net/ipv4/ipmr_base.c:313 RCU-list traversed in non-reader section!!

	rcu_scheduler_active = 2, debug_locks = 1
		   2 locks held by RetransmitAggre/3519:
		    #0: ffff88816188c6c0 (nlk_cb_mutex-ROUTE){+.+.}-{3:3}, at: __netlink_dump_start+0x8a/0x290
		    #1: ffffffff83fcf7a8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_dumpit+0x6b/0x90

	stack backtrace:
		    lockdep_rcu_suspicious
		    mr_table_dump
		    ipmr_rtm_dumproute
		    rtnl_dump_all
		    rtnl_dumpit
		    netlink_dump
		    __netlink_dump_start
		    rtnetlink_rcv_msg
		    netlink_rcv_skb
		    netlink_unicast
		    netlink_sendmsg

This is not a problem per see, since the RTNL lock is held here, so, it
is safe to iterate in the list without the RCU read lock, as suggested
by Eric.

To alleviate the concern, modify the code to use
list_for_each_entry_rcu() with the RTNL-held argument.

The annotation will raise an error only if RTNL or RCU read lock are
missing during iteration, signaling a legitimate problem, otherwise it
will avoid this false positive.

This will solve the IPv6 case as well, since ip6mr_rtm_dumproute() calls
this function as well.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20241108-ipmr_rcu-v2-1-c718998e209b@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv4/ipmr_base.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ipmr_base.c b/net/ipv4/ipmr_base.c
index ea48bd15a575b..4a1a90a135406 100644
--- a/net/ipv4/ipmr_base.c
+++ b/net/ipv4/ipmr_base.c
@@ -301,7 +301,8 @@ int mr_table_dump(struct mr_table *mrt, struct sk_buff *skb,
 	if (filter->filter_set)
 		flags |= NLM_F_DUMP_FILTERED;
 
-	list_for_each_entry_rcu(mfc, &mrt->mfc_cache_list, list) {
+	list_for_each_entry_rcu(mfc, &mrt->mfc_cache_list, list,
+				lockdep_rtnl_is_held()) {
 		if (e < s_e)
 			goto next_entry;
 		if (filter->dev &&
-- 
2.43.0