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mm: userfaultfd: remove stale comment about core dump locking 

Since commit 7f3bfab52c ("mm/gup: take mmap_lock in get_dump_page()"),
which landed in v5.10, core dumping doesn't enter fault handling without
holding the mmap_lock anymore.  Remove the stale parts of the comments,
but leave the behavior as-is - letting core dumping block on userfault
handling would be a bad idea and could lead to deadlocks if the dumping
process was handling its own userfaults.

Link: https://lkml.kernel.org/r/20230815212216.264445-1-jannh@google.com
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jann Horn 2023-08-15 23:22:16 +02:00 committed by Andrew Morton
parent 00de2c9f26
commit 004a9a38e2
1 changed files with 1 additions and 5 deletions
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6
fs/userfaultfd.c
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@ -428,15 +428,11 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
* FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
* the no_page_table() helper in follow_page_mask(), but the
* shmem_vm_ops->fault method is invoked even during
* coredumping without mmap_lock and it ends up here.
* coredumping and it ends up here.
*/
if (current->flags & (PF_EXITING|PF_DUMPCORE))
goto out;
/*
* Coredumping runs without mmap_lock so we can only check that
* the mmap_lock is held, if PF_DUMPCORE was not set.
*/
assert_fault_locked(vmf);
ctx = vma->vm_userfaultfd_ctx.ctx;