From: Song Liu songliubraving@fb.com
[ Upstream commit d44248a41337731a111374822d7d4451b64e73e4 ]
perf_mmap() always increases user->locked_vm. As a result, "extra" could grow bigger than "user_extra", which doesn't make sense. Here is an example case:
(Note: Assume "user_lock_limit" is very small.)
| # of perf_mmap calls |vma->vm_mm->pinned_vm|user->locked_vm| | 0 | 0 | 0 | | 1 | user_extra | user_extra | | 2 | 3 * user_extra | 2 * user_extra| | 3 | 6 * user_extra | 3 * user_extra| | 4 | 10 * user_extra | 4 * user_extra|
Fix this by maintaining proper user_extra and extra.
Reviewed-By: Hechao Li hechaol@fb.com Reported-by: Hechao Li hechaol@fb.com Signed-off-by: Song Liu songliubraving@fb.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: kernel-team@fb.com Cc: Jie Meng jmeng@fb.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: https://lkml.kernel.org/r/20190904214618.3795672-1-songliubraving@fb.com Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/events/core.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 0463c1151baeb..a0120bdbce177 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5585,7 +5585,8 @@ static void perf_mmap_close(struct vm_area_struct *vma) * undo the VM accounting. */
- atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm); + atomic_long_sub((size >> PAGE_SHIFT) + 1 - mmap_locked, + &mmap_user->locked_vm); atomic64_sub(mmap_locked, &vma->vm_mm->pinned_vm); free_uid(mmap_user);
@@ -5729,8 +5730,20 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
user_locked = atomic_long_read(&user->locked_vm) + user_extra;
- if (user_locked > user_lock_limit) + if (user_locked <= user_lock_limit) { + /* charge all to locked_vm */ + } else if (atomic_long_read(&user->locked_vm) >= user_lock_limit) { + /* charge all to pinned_vm */ + extra = user_extra; + user_extra = 0; + } else { + /* + * charge locked_vm until it hits user_lock_limit; + * charge the rest from pinned_vm + */ extra = user_locked - user_lock_limit; + user_extra -= extra; + }
lock_limit = rlimit(RLIMIT_MEMLOCK); lock_limit >>= PAGE_SHIFT;