From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults 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 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) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- include/net/compat.h | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 include/net/compat.h (limited to 'include/net/compat.h') diff --git a/include/net/compat.h b/include/net/compat.h new file mode 100644 index 000000000..84c163f40 --- /dev/null +++ b/include/net/compat.h @@ -0,0 +1,95 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef NET_COMPAT_H +#define NET_COMPAT_H + + +struct sock; + +#include + +struct compat_msghdr { + compat_uptr_t msg_name; /* void * */ + compat_int_t msg_namelen; + compat_uptr_t msg_iov; /* struct compat_iovec * */ + compat_size_t msg_iovlen; + compat_uptr_t msg_control; /* void * */ + compat_size_t msg_controllen; + compat_uint_t msg_flags; +}; + +struct compat_mmsghdr { + struct compat_msghdr msg_hdr; + compat_uint_t msg_len; +}; + +struct compat_cmsghdr { + compat_size_t cmsg_len; + compat_int_t cmsg_level; + compat_int_t cmsg_type; +}; + +struct compat_rtentry { + u32 rt_pad1; + struct sockaddr rt_dst; /* target address */ + struct sockaddr rt_gateway; /* gateway addr (RTF_GATEWAY) */ + struct sockaddr rt_genmask; /* target network mask (IP) */ + unsigned short rt_flags; + short rt_pad2; + u32 rt_pad3; + unsigned char rt_tos; + unsigned char rt_class; + short rt_pad4; + short rt_metric; /* +1 for binary compatibility! */ + compat_uptr_t rt_dev; /* forcing the device at add */ + u32 rt_mtu; /* per route MTU/Window */ + u32 rt_window; /* Window clamping */ + unsigned short rt_irtt; /* Initial RTT */ +}; + +int __get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr *msg, + struct sockaddr __user **save_addr); +int get_compat_msghdr(struct msghdr *, struct compat_msghdr __user *, + struct sockaddr __user **, struct iovec **); +int put_cmsg_compat(struct msghdr*, int, int, int, void *); + +int cmsghdr_from_user_compat_to_kern(struct msghdr *, struct sock *, + unsigned char *, int); + +struct compat_group_req { + __u32 gr_interface; + struct __kernel_sockaddr_storage gr_group + __aligned(4); +} __packed; + +struct compat_group_source_req { + __u32 gsr_interface; + struct __kernel_sockaddr_storage gsr_group + __aligned(4); + struct __kernel_sockaddr_storage gsr_source + __aligned(4); +} __packed; + +struct compat_group_filter { + union { + struct { + __u32 gf_interface_aux; + struct __kernel_sockaddr_storage gf_group_aux + __aligned(4); + __u32 gf_fmode_aux; + __u32 gf_numsrc_aux; + struct __kernel_sockaddr_storage gf_slist[1] + __aligned(4); + } __packed; + struct { + __u32 gf_interface; + struct __kernel_sockaddr_storage gf_group + __aligned(4); + __u32 gf_fmode; + __u32 gf_numsrc; + struct __kernel_sockaddr_storage gf_slist_flex[] + __aligned(4); + } __packed; + }; +} __packed; + +#endif /* NET_COMPAT_H */ -- cgit v1.3.1