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authorCheng Jui Wang <cheng-jui.wang@mediatek.com>2022-02-10 13:50:11 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-02-23 14:03:22 +0300
commit5dcc365697340599b7ef63a9352fcea890f0e78b (patch)
treedeef36984f2269c16dd1dbbbe83f5ef60ed5c9c1 /kernel
parentc2df4c62a1898bd38bbb2c7521da9e4ad0ec7f8a (diff)
downloadlinux-5dcc365697340599b7ef63a9352fcea890f0e78b.tar.xz
lockdep: Correct lock_classes index mapping
commit 28df029d53a2fd80c1b8674d47895648ad26dcfb upstream. A kernel exception was hit when trying to dump /proc/lockdep_chains after lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!": Unable to handle kernel paging request at virtual address 00054005450e05c3 ... 00054005450e05c3] address between user and kernel address ranges ... pc : [0xffffffece769b3a8] string+0x50/0x10c lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c ... Call trace: string+0x50/0x10c vsnprintf+0x468/0x69c seq_printf+0x8c/0xd8 print_name+0x64/0xf4 lc_show+0xb8/0x128 seq_read_iter+0x3cc/0x5fc proc_reg_read_iter+0xdc/0x1d4 The cause of the problem is the function lock_chain_get_class() will shift lock_classes index by 1, but the index don't need to be shifted anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range of class_idx in held_lock struct") already change the index to start from 0. The lock_classes[-1] located at chain_hlocks array. When printing lock_classes[-1] after the chain_hlocks entries are modified, the exception happened. The output of lockdep_chains are incorrect due to this problem too. Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey") Signed-off-by: Cheng Jui Wang <cheng-jui.wang@mediatek.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Link: https://lore.kernel.org/r/20220210105011.21712-1-cheng-jui.wang@mediatek.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/locking/lockdep.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index d624231eab2b..92127296cf2b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3450,7 +3450,7 @@ struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
u16 chain_hlock = chain_hlocks[chain->base + i];
unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
- return lock_classes + class_idx - 1;
+ return lock_classes + class_idx;
}
/*
@@ -3518,7 +3518,7 @@ static void print_chain_keys_chain(struct lock_chain *chain)
hlock_id = chain_hlocks[chain->base + i];
chain_key = print_chain_key_iteration(hlock_id, chain_key);
- print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
+ print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
printk("\n");
}
}