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    Subject[PATCH 5.9 114/757] lockdep: Fix usage_traceoverflow
    Date
    From: Peter Zijlstra <peterz@infradead.org>

    [ Upstream commit 2bb8945bcc1a768f2bc402a16c9610bba8d5187d ]

    Basically print_lock_class_header()'s for loop is out of sync with the
    the size of of ->usage_traces[].

    Also clean things up a bit while at it, to avoid such mishaps in the future.

    Fixes: 23870f122768 ("locking/lockdep: Fix "USED" <- "IN-NMI" inversions")
    Reported-by: Qian Cai <cai@redhat.com>
    Debugged-by: Boqun Feng <boqun.feng@gmail.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Tested-by: Qian Cai <cai@redhat.com>
    Link: https://lkml.kernel.org/r/20200930094937.GE2651@hirez.programming.kicks-ass.net
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/lockdep_types.h | 8 ++++++--
    kernel/locking/lockdep.c | 32 ++++++++++++++----------------
    kernel/locking/lockdep_internals.h | 7 +++++--
    3 files changed, 26 insertions(+), 21 deletions(-)

    diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
    index bb35b449f5330..9a1fd49df17f6 100644
    --- a/include/linux/lockdep_types.h
    +++ b/include/linux/lockdep_types.h
    @@ -35,8 +35,12 @@ enum lockdep_wait_type {
    /*
    * We'd rather not expose kernel/lockdep_states.h this wide, but we do need
    * the total number of states... :-(
    + *
    + * XXX_LOCK_USAGE_STATES is the number of lines in lockdep_states.h, for each
    + * of those we generates 4 states, Additionally we report on USED and USED_READ.
    */
    -#define XXX_LOCK_USAGE_STATES (1+2*4)
    +#define XXX_LOCK_USAGE_STATES 2
    +#define LOCK_TRACE_STATES (XXX_LOCK_USAGE_STATES*4 + 2)

    /*
    * NR_LOCKDEP_CACHING_CLASSES ... Number of classes
    @@ -106,7 +110,7 @@ struct lock_class {
    * IRQ/softirq usage tracking bits:
    */
    unsigned long usage_mask;
    - const struct lock_trace *usage_traces[XXX_LOCK_USAGE_STATES];
    + const struct lock_trace *usage_traces[LOCK_TRACE_STATES];

    /*
    * Generation counter, when doing certain classes of graph walking,
    diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
    index 2facbbd146ec2..a430fbb01eb16 100644
    --- a/kernel/locking/lockdep.c
    +++ b/kernel/locking/lockdep.c
    @@ -585,6 +585,8 @@ static const char *usage_str[] =
    #include "lockdep_states.h"
    #undef LOCKDEP_STATE
    [LOCK_USED] = "INITIAL USE",
    + [LOCK_USED_READ] = "INITIAL READ USE",
    + /* abused as string storage for verify_lock_unused() */
    [LOCK_USAGE_STATES] = "IN-NMI",
    };
    #endif
    @@ -1939,7 +1941,7 @@ static void print_lock_class_header(struct lock_class *class, int depth)
    #endif
    printk(KERN_CONT " {\n");

    - for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
    + for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
    if (class->usage_mask & (1 << bit)) {
    int len = depth;

    @@ -3969,7 +3971,7 @@ static int separate_irq_context(struct task_struct *curr,
    static int mark_lock(struct task_struct *curr, struct held_lock *this,
    enum lock_usage_bit new_bit)
    {
    - unsigned int old_mask, new_mask, ret = 1;
    + unsigned int new_mask, ret = 1;

    if (new_bit >= LOCK_USAGE_STATES) {
    DEBUG_LOCKS_WARN_ON(1);
    @@ -3996,30 +3998,26 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
    if (unlikely(hlock_class(this)->usage_mask & new_mask))
    goto unlock;

    - old_mask = hlock_class(this)->usage_mask;
    hlock_class(this)->usage_mask |= new_mask;

    - /*
    - * Save one usage_traces[] entry and map both LOCK_USED and
    - * LOCK_USED_READ onto the same entry.
    - */
    - if (new_bit == LOCK_USED || new_bit == LOCK_USED_READ) {
    - if (old_mask & (LOCKF_USED | LOCKF_USED_READ))
    - goto unlock;
    - new_bit = LOCK_USED;
    + if (new_bit < LOCK_TRACE_STATES) {
    + if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
    + return 0;
    }

    - if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
    - return 0;
    -
    switch (new_bit) {
    + case 0 ... LOCK_USED-1:
    + ret = mark_lock_irq(curr, this, new_bit);
    + if (!ret)
    + return 0;
    + break;
    +
    case LOCK_USED:
    debug_atomic_dec(nr_unused_locks);
    break;
    +
    default:
    - ret = mark_lock_irq(curr, this, new_bit);
    - if (!ret)
    - return 0;
    + break;
    }

    unlock:
    diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
    index b0be1560ed17a..de49f9e1c11ba 100644
    --- a/kernel/locking/lockdep_internals.h
    +++ b/kernel/locking/lockdep_internals.h
    @@ -20,9 +20,12 @@ enum lock_usage_bit {
    #undef LOCKDEP_STATE
    LOCK_USED,
    LOCK_USED_READ,
    - LOCK_USAGE_STATES
    + LOCK_USAGE_STATES,
    };

    +/* states after LOCK_USED_READ are not traced and printed */
    +static_assert(LOCK_TRACE_STATES == LOCK_USAGE_STATES);
    +
    #define LOCK_USAGE_READ_MASK 1
    #define LOCK_USAGE_DIR_MASK 2
    #define LOCK_USAGE_STATE_MASK (~(LOCK_USAGE_READ_MASK | LOCK_USAGE_DIR_MASK))
    @@ -121,7 +124,7 @@ static const unsigned long LOCKF_USED_IN_IRQ_READ =
    extern struct list_head all_lock_classes;
    extern struct lock_chain lock_chains[];

    -#define LOCK_USAGE_CHARS (1+LOCK_USAGE_STATES/2)
    +#define LOCK_USAGE_CHARS (2*XXX_LOCK_USAGE_STATES + 1)

    extern void get_usage_chars(struct lock_class *class,
    char usage[LOCK_USAGE_CHARS]);
    --
    2.25.1


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