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 --- net/batman-adv/bitarray.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 net/batman-adv/bitarray.c (limited to 'net/batman-adv/bitarray.c') diff --git a/net/batman-adv/bitarray.c b/net/batman-adv/bitarray.c new file mode 100644 index 000000000..67cb35633 --- /dev/null +++ b/net/batman-adv/bitarray.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) B.A.T.M.A.N. contributors: + * + * Simon Wunderlich, Marek Lindner + */ + +#include "bitarray.h" +#include "main.h" + +#include + +#include "log.h" + +/* shift the packet array by n places. */ +static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n) +{ + if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE) + return; + + bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE); +} + +/** + * batadv_bit_get_packet() - receive and process one packet within the sequence + * number window + * @priv: the bat priv with all the mesh interface information + * @seq_bits: pointer to the sequence number bitmap of received packets + * @seq_num_diff: difference between the current/received sequence number and + * the last sequence number + * @set_mark: whether this packet should be marked in seq_bits + * + * Return: true if the window was moved (either new or very old), + * false if the window was not moved/shifted. + */ +bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits, + s32 seq_num_diff, int set_mark) +{ + struct batadv_priv *bat_priv = priv; + + /* sequence number is slightly older. We already got a sequence number + * higher than this one, so we just mark it. + */ + if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) { + if (set_mark) + batadv_set_bit(seq_bits, -seq_num_diff); + return false; + } + + /* sequence number is slightly newer, so we shift the window and + * set the mark if required + */ + if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) { + batadv_bitmap_shift_left(seq_bits, seq_num_diff); + + if (set_mark) + batadv_set_bit(seq_bits, 0); + return true; + } + + /* sequence number is much newer, probably missed a lot of packets */ + if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE && + seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) { + batadv_dbg(BATADV_DBG_BATMAN, bat_priv, + "We missed a lot of packets (%i) !\n", + seq_num_diff - 1); + bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); + if (set_mark) + batadv_set_bit(seq_bits, 0); + return true; + } + + /* received a much older packet. The other host either restarted + * or the old packet got delayed somewhere in the network. The + * packet should be dropped without calling this function if the + * seqno window is protected. + * + * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE + * or + * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE + */ + batadv_dbg(BATADV_DBG_BATMAN, bat_priv, + "Other host probably restarted!\n"); + + bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE); + if (set_mark) + batadv_set_bit(seq_bits, 0); + + return true; +} -- cgit v1.3.1