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authorSong Liu <songliubraving@fb.com>2020-01-23 10:11:46 -0800
committerIngo Molnar <mingo@kernel.org>2020-01-28 21:20:18 +0100
commit003461559ef7a9bd0239bae35a22ad8924d6e9ad (patch)
tree9121b588c0ec57dbd78ff7186e218b4d3d59e20a /kernel/events
parentb0be0eff1a5ab77d588b76bd8b1c92d5d17b3f73 (diff)
perf/core: Fix mlock accounting in perf_mmap()
Decreasing sysctl_perf_event_mlock between two consecutive perf_mmap()s of a perf ring buffer may lead to an integer underflow in locked memory accounting. This may lead to the undesired behaviors, such as failures in BPF map creation. Address this by adjusting the accounting logic to take into account the possibility that the amount of already locked memory may exceed the current limit. Fixes: c4b75479741c ("perf/core: Make the mlock accounting simple again") Suggested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: <stable@vger.kernel.org> Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Link: https://lkml.kernel.org/r/20200123181146.2238074-1-songliubraving@fb.com
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2173c23c25b4..2d9aeba1f3e2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5916,7 +5916,15 @@ accounting:
*/
user_lock_limit *= num_online_cpus();
- user_locked = atomic_long_read(&user->locked_vm) + user_extra;
+ user_locked = atomic_long_read(&user->locked_vm);
+
+ /*
+ * sysctl_perf_event_mlock may have changed, so that
+ * user->locked_vm > user_lock_limit
+ */
+ if (user_locked > user_lock_limit)
+ user_locked = user_lock_limit;
+ user_locked += user_extra;
if (user_locked > user_lock_limit) {
/*