https://github.com/torvalds/linux
Revision df17277b2a85c00f5710e33ce238ba4114687a28 authored by Mike Rapoport on 01 June 2019, 05:30:33 UTC, committed by Linus Torvalds on 01 June 2019, 22:51:31 UTC
When get_user_pages*() is called with pages = NULL, the processing of VM_FAULT_RETRY terminates early without actually retrying to fault-in all the pages. If the pages in the requested range belong to a VMA that has userfaultfd registered, handle_userfault() returns VM_FAULT_RETRY *after* user space has populated the page, but for the gup pre-fault case there's no actual retry and the caller will get no pages although they are present. This issue was uncovered when running post-copy memory restore in CRIU after d9c9ce34ed5c ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails"). After this change, the copying of FPU state to the sigframe switched from copy_to_user() variants which caused a real page fault to get_user_pages() with pages parameter set to NULL. In post-copy mode of CRIU, the destination memory is managed with userfaultfd and lack of the retry for pre-fault case in get_user_pages() causes a crash of the restored process. Making the pre-fault behavior of get_user_pages() the same as the "normal" one fixes the issue. Link: http://lkml.kernel.org/r/1557844195-18882-1-git-send-email-rppt@linux.ibm.com Fixes: d9c9ce34ed5c ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails") Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> Tested-by: Andrei Vagin <avagin@gmail.com> [https://travis-ci.org/avagin/linux/builds/533184940] Tested-by: Hugh Dickins <hughd@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Borislav Petkov <bp@suse.de> Cc: Pavel Machek <pavel@ucw.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent b9fba67
Tip revision: df17277b2a85c00f5710e33ce238ba4114687a28 authored by Mike Rapoport on 01 June 2019, 05:30:33 UTC
mm/gup: continue VM_FAULT_RETRY processing even for pre-faults
mm/gup: continue VM_FAULT_RETRY processing even for pre-faults
Tip revision: df17277
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certs | ||
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kernel | ||
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net | ||
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.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
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.gitignore | -rw-r--r-- | 1.6 KB |
.mailmap | -rw-r--r-- | 11.9 KB |
COPYING | -rw-r--r-- | 423 bytes |
CREDITS | -rw-r--r-- | 96.9 KB |
Kbuild | -rw-r--r-- | 1.5 KB |
Kconfig | -rw-r--r-- | 563 bytes |
MAINTAINERS | -rw-r--r-- | 498.9 KB |
Makefile | -rw-r--r-- | 58.8 KB |
README | -rw-r--r-- | 727 bytes |
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