ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faultsgrafted

When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set,
a user fault may trigger show_pte() without any lock.
If another thread in the same process concurrently calls munmap(),
the page table pages may be freed while show_pte() is still traversing
them, causing a use-after-free in show_pte().

If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table
of PMD are freed when show_pte() is running.

Acquire mmap_write_lock() around show_pte() for user faults to fix the
contention.

For user faults, additionally restrict that show_pte() is called only
when the addr is a user-space address (addr < TASK_SIZE). This is because
the lock of tsk->mm only protects the virtual memory of user address space,
furthermore, dumping the page tables of a kernel-space address for user
faults is unnecessary and may have security implications.

Keep everything unchanged for kernel faults, because the kernel is
already in the "oops" state, acquiring a lock may risk a deadlock.

Co-developed-by: Qi Xi <xiqi2@huawei.com>

Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults")
Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 77 insertions, 0 deletions

diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
new file mode 100644
index 000000000..06e21c26b
--- /dev/null
+++ b/net/ipv4/Makefile
@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux TCP/IP (INET) layer.
+#
+
+obj-y     := route.o inetpeer.o protocol.o \
+	     ip_input.o ip_fragment.o ip_forward.o ip_options.o \
+	     ip_output.o ip_sockglue.o inet_hashtables.o \
+	     inet_timewait_sock.o inet_connection_sock.o \
+	     tcp.o tcp_input.o tcp_output.o tcp_timer.o tcp_ipv4.o \
+	     tcp_minisocks.o tcp_cong.o tcp_metrics.o tcp_fastopen.o \
+	     tcp_recovery.o tcp_ulp.o \
+	     tcp_offload.o tcp_plb.o datagram.o raw.o udp.o \
+	     udp_offload.o arp.o icmp.o devinet.o af_inet.o igmp.o \
+	     fib_frontend.o fib_semantics.o fib_trie.o fib_notifier.o \
+	     inet_fragment.o ping.o ip_tunnel_core.o gre_offload.o \
+	     metrics.o netlink.o nexthop.o udp_tunnel_stub.o
+
+obj-$(CONFIG_NET_IP_TUNNEL) += ip_tunnel.o
+obj-$(CONFIG_SYSCTL) += sysctl_net_ipv4.o
+obj-$(CONFIG_PROC_FS) += proc.o
+obj-$(CONFIG_IP_MULTIPLE_TABLES) += fib_rules.o
+obj-$(CONFIG_IP_MROUTE) += ipmr.o
+obj-$(CONFIG_IP_MROUTE_COMMON) += ipmr_base.o
+obj-$(CONFIG_NET_IPIP) += ipip.o
+gre-y := gre_demux.o
+fou-y := fou_core.o fou_nl.o fou_bpf.o
+obj-$(CONFIG_NET_FOU) += fou.o
+obj-$(CONFIG_NET_IPGRE_DEMUX) += gre.o
+obj-$(CONFIG_NET_IPGRE) += ip_gre.o
+udp_tunnel-y := udp_tunnel_core.o udp_tunnel_nic.o
+obj-$(CONFIG_NET_UDP_TUNNEL) += udp_tunnel.o
+obj-$(CONFIG_NET_IPVTI) += ip_vti.o
+obj-$(CONFIG_SYN_COOKIES) += syncookies.o
+obj-$(CONFIG_INET_AH) += ah4.o
+obj-$(CONFIG_INET_ESP) += esp4.o
+obj-$(CONFIG_INET_ESP_OFFLOAD) += esp4_offload.o
+obj-$(CONFIG_INET_IPCOMP) += ipcomp.o
+obj-$(CONFIG_INET_XFRM_TUNNEL) += xfrm4_tunnel.o
+obj-$(CONFIG_INET_TUNNEL) += tunnel4.o
+obj-$(CONFIG_IP_PNP) += ipconfig.o
+obj-$(CONFIG_NETFILTER)	+= netfilter.o netfilter/
+obj-$(CONFIG_INET_DIAG) += inet_diag.o
+obj-$(CONFIG_INET_TCP_DIAG) += tcp_diag.o
+obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o
+obj-$(CONFIG_INET_RAW_DIAG) += raw_diag.o
+obj-$(CONFIG_TCP_CONG_BBR) += tcp_bbr.o
+obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
+obj-$(CONFIG_TCP_CONG_CDG) += tcp_cdg.o
+obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o
+obj-$(CONFIG_TCP_CONG_DCTCP) += tcp_dctcp.o
+obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o
+obj-$(CONFIG_TCP_CONG_HSTCP) += tcp_highspeed.o
+obj-$(CONFIG_TCP_CONG_HYBLA) += tcp_hybla.o
+obj-$(CONFIG_TCP_CONG_HTCP) += tcp_htcp.o
+obj-$(CONFIG_TCP_CONG_VEGAS) += tcp_vegas.o
+obj-$(CONFIG_TCP_CONG_NV) += tcp_nv.o
+obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
+obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
+obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
+obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
+obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
+obj-$(CONFIG_NET_SOCK_MSG) += tcp_bpf.o
+obj-$(CONFIG_BPF_SYSCALL) += udp_bpf.o
+obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
+
+obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
+		      xfrm4_output.o xfrm4_protocol.o
+obj-$(CONFIG_TCP_AO) += tcp_ao.o
+
+ifeq ($(CONFIG_BPF_JIT),y)
+obj-$(CONFIG_BPF_SYSCALL) += bpf_tcp_ca.o
+endif
+
+ifdef CONFIG_GCOV_PROFILE_NETFILTER
+GCOV_PROFILE_netfilter.o := y
+endif