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7d6be67cfd
Commit2b5067a814("mm: mmap_lock: add tracepoints around lock acquisition") introduced TRACE_MMAP_LOCK_EVENT() macro using preempt_disable() in order to let get_mm_memcg_path() return a percpu buffer exclusively used by normal, softirq, irq and NMI contexts respectively. Commit832b507253("mm: mmap_lock: use local locks instead of disabling preemption") replaced preempt_disable() with local_lock(&memcg_paths.lock) based on an argument that preempt_disable() has to be avoided because get_mm_memcg_path() might sleep if PREEMPT_RT=y. But syzbot started reporting inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage. and inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. messages, for local_lock() does not disable IRQ. We could replace local_lock() with local_lock_irqsave() in order to suppress these messages. But this patch instead replaces percpu buffers with on-stack buffer, for the size of each buffer returned by get_memcg_path_buf() is only 256 bytes which is tolerable for allocating from current thread's kernel stack memory. Link: https://lkml.kernel.org/r/ef22d289-eadb-4ed9-863b-fbc922b33d8d@I-love.SAKURA.ne.jp Reported-by: syzbot <syzbot+40905bca570ae6784745@syzkaller.appspotmail.com> Closes: https://syzkaller.appspot.com/bug?extid=40905bca570ae6784745 Fixes:832b507253("mm: mmap_lock: use local locks instead of disabling preemption") Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reviewed-by: Axel Rasmussen <axelrasmussen@google.com> Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
111 lines
2.8 KiB
C
111 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define CREATE_TRACE_POINTS
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#include <trace/events/mmap_lock.h>
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#include <linux/mm.h>
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#include <linux/cgroup.h>
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#include <linux/memcontrol.h>
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#include <linux/mmap_lock.h>
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#include <linux/mutex.h>
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#include <linux/percpu.h>
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#include <linux/rcupdate.h>
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#include <linux/smp.h>
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#include <linux/trace_events.h>
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#include <linux/local_lock.h>
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EXPORT_TRACEPOINT_SYMBOL(mmap_lock_start_locking);
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EXPORT_TRACEPOINT_SYMBOL(mmap_lock_acquire_returned);
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EXPORT_TRACEPOINT_SYMBOL(mmap_lock_released);
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#ifdef CONFIG_MEMCG
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static atomic_t reg_refcount;
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/*
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* Size of the buffer for memcg path names. Ignoring stack trace support,
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* trace_events_hist.c uses MAX_FILTER_STR_VAL for this, so we also use it.
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*/
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#define MEMCG_PATH_BUF_SIZE MAX_FILTER_STR_VAL
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int trace_mmap_lock_reg(void)
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{
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atomic_inc(®_refcount);
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return 0;
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}
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void trace_mmap_lock_unreg(void)
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{
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atomic_dec(®_refcount);
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}
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#define TRACE_MMAP_LOCK_EVENT(type, mm, ...) \
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do { \
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char buf[MEMCG_PATH_BUF_SIZE]; \
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get_mm_memcg_path(mm, buf, sizeof(buf)); \
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trace_mmap_lock_##type(mm, buf, ##__VA_ARGS__); \
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} while (0)
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#else /* !CONFIG_MEMCG */
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int trace_mmap_lock_reg(void)
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{
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return 0;
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}
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void trace_mmap_lock_unreg(void)
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{
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}
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#define TRACE_MMAP_LOCK_EVENT(type, mm, ...) \
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trace_mmap_lock_##type(mm, "", ##__VA_ARGS__)
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#endif /* CONFIG_MEMCG */
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#ifdef CONFIG_TRACING
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#ifdef CONFIG_MEMCG
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/*
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* Write the given mm_struct's memcg path to a buffer. If the path cannot be
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* determined or the trace event is being unregistered, empty string is written.
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*/
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static void get_mm_memcg_path(struct mm_struct *mm, char *buf, size_t buflen)
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{
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struct mem_cgroup *memcg;
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buf[0] = '\0';
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/* No need to get path if no trace event is registered. */
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if (!atomic_read(®_refcount))
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return;
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memcg = get_mem_cgroup_from_mm(mm);
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if (memcg == NULL)
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return;
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if (memcg->css.cgroup)
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cgroup_path(memcg->css.cgroup, buf, buflen);
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css_put(&memcg->css);
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}
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#endif /* CONFIG_MEMCG */
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/*
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* Trace calls must be in a separate file, as otherwise there's a circular
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* dependency between linux/mmap_lock.h and trace/events/mmap_lock.h.
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*/
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void __mmap_lock_do_trace_start_locking(struct mm_struct *mm, bool write)
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{
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TRACE_MMAP_LOCK_EVENT(start_locking, mm, write);
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}
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EXPORT_SYMBOL(__mmap_lock_do_trace_start_locking);
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void __mmap_lock_do_trace_acquire_returned(struct mm_struct *mm, bool write,
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bool success)
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{
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TRACE_MMAP_LOCK_EVENT(acquire_returned, mm, write, success);
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}
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EXPORT_SYMBOL(__mmap_lock_do_trace_acquire_returned);
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void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write)
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{
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TRACE_MMAP_LOCK_EVENT(released, mm, write);
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}
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EXPORT_SYMBOL(__mmap_lock_do_trace_released);
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#endif /* CONFIG_TRACING */
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