https://github.com/torvalds/linux
Revision 64c2b20301f62c697352c8028c569b1b2bdd8e82 authored by Andrea Arcangeli on 16 June 2017, 21:02:37 UTC, committed by Linus Torvalds on 16 June 2017, 21:37:05 UTC
Anon and hugetlbfs handle FOLL_DUMP set by get_dump_page() internally to __get_user_pages(). shmem as opposed has no special FOLL_DUMP handling there so handle_mm_fault() is invoked without mmap_sem and ends up calling handle_userfault() that isn't expecting to be invoked without mmap_sem held. This makes handle_userfault() fail immediately if invoked through shmem_vm_ops->fault during coredumping and solves the problem. The side effect is a BUG_ON with no lock held triggered by the coredumping process which exits. Only 4.11 is affected, pre-4.11 anon memory holes are skipped in __get_user_pages by checking FOLL_DUMP explicitly against empty pagetables (mm/gup.c:no_page_table()). It's zero cost as we already had a check for current->flags to prevent futex to trigger userfaults during exit (PF_EXITING). Link: http://lkml.kernel.org/r/20170615214838.27429-1-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: <stable@vger.kernel.org> [4.11+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tip revision: 64c2b20301f62c697352c8028c569b1b2bdd8e82 authored by Andrea Arcangeli on 16 June 2017, 21:02:37 UTC
userfaultfd: shmem: handle coredumping in handle_userfault()
userfaultfd: shmem: handle coredumping in handle_userfault()
Tip revision: 64c2b20
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crypto | ||
drivers | ||
firmware | ||
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include | ||
init | ||
ipc | ||
kernel | ||
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net | ||
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.gitattributes | -rw-r--r-- | 30 bytes |
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COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 96.2 KB |
Kbuild | -rw-r--r-- | 2.2 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 397.7 KB |
Makefile | -rw-r--r-- | 58.6 KB |
README | -rw-r--r-- | 722 bytes |
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