redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity
Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
882,102 Commits
15 Branches
0 Tags
3.4 GiB
C 97.7%
Assembly 1.4%
Makefile 0.3%
Shell 0.2%
Python 0.1%
Other 0.1%
 
 
 
 
 
 
Go to file
Vasily Gorbik 4f5260ee0c mm/gup: fix gup_fast with dynamic page table folding 
commit d3f7b1bb20 upstream.

Currently to make sure that every page table entry is read just once
gup_fast walks perform READ_ONCE and pass pXd value down to the next
gup_pXd_range function by value e.g.:

  static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
                           unsigned int flags, struct page **pages, int *nr)
  ...
          pudp = pud_offset(&p4d, addr);

This function passes a reference on that local value copy to pXd_offset,
and might get the very same pointer in return.  This happens when the
level is folded (on most arches), and that pointer should not be
iterated.

On s390 due to the fact that each task might have different 5,4 or
3-level address translation and hence different levels folded the logic
is more complex and non-iteratable pointer to a local copy leads to
severe problems.

Here is an example of what happens with gup_fast on s390, for a task
with 3-level paging, crossing a 2 GB pud boundary:

  // addr = 0x1007ffff000, end = 0x10080001000
  static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
                           unsigned int flags, struct page **pages, int *nr)
  {
        unsigned long next;
        pud_t *pudp;

        // pud_offset returns &p4d itself (a pointer to a value on stack)
        pudp = pud_offset(&p4d, addr);
        do {
                // on second iteratation reading "random" stack value
                pud_t pud = READ_ONCE(*pudp);

                // next = 0x10080000000, due to PUD_SIZE/MASK != PGDIR_SIZE/MASK on s390
                next = pud_addr_end(addr, end);
                ...
        } while (pudp++, addr = next, addr != end); // pudp++ iterating over stack

        return 1;
  }

This happens since s390 moved to common gup code with commit
d1874a0c28 ("s390/mm: make the pxd_offset functions more robust") and
commit 1a42010cdc ("s390/mm: convert to the generic
get_user_pages_fast code").

s390 tried to mimic static level folding by changing pXd_offset
primitives to always calculate top level page table offset in pgd_offset
and just return the value passed when pXd_offset has to act as folded.

What is crucial for gup_fast and what has been overlooked is that
PxD_SIZE/MASK and thus pXd_addr_end should also change correspondingly.
And the latter is not possible with dynamic folding.

To fix the issue in addition to pXd values pass original pXdp pointers
down to gup_pXd_range functions.  And introduce pXd_offset_lockless
helpers, which take an additional pXd entry value parameter.  This has
already been discussed in

  https://lkml.kernel.org/r/20190418100218.0a4afd51@mschwideX1

Fixes: 1a42010cdc ("s390/mm: convert to the generic get_user_pages_fast code")
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: <stable@vger.kernel.org>	[5.2+]
Link: https://lkml.kernel.org/r/patch.git-943f1e5dcff2.your-ad-here.call-01599856292-ext-8676@work.hours
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-10-01 13:18:24 +02:00
Documentation dt-bindings: sound: wm8994: Correct required supplies based on actual implementaion 2020-10-01 13:17:58 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch mm/gup: fix gup_fast with dynamic page table folding 2020-10-01 13:18:24 +02:00
block block: only call sched requeue_request() for scheduled requests 2020-09-23 12:40:37 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: af_alg - Work around empty control messages without MSG_MORE 2020-09-03 11:27:05 +02:00
drivers dmabuf: fix NULL pointer dereference in dma_buf_release() 2020-10-01 13:18:24 +02:00
fs btrfs: fix overflow when copying corrupt csums for a message 2020-10-01 13:18:24 +02:00
include mm/gup: fix gup_fast with dynamic page table folding 2020-10-01 13:18:24 +02:00
init kprobes: tracing/kprobes: Fix to kill kprobes on initmem after boot 2020-10-01 13:18:23 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel kprobes: tracing/kprobes: Fix to kill kprobes on initmem after boot 2020-10-01 13:18:23 +02:00
lib lib/string.c: implement stpcpy 2020-10-01 13:18:23 +02:00
mm mm/gup: fix gup_fast with dynamic page table folding 2020-10-01 13:18:24 +02:00
net lib80211: fix unmet direct dependendices config warning when !CRYPTO 2020-10-01 13:18:20 +02:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts checkpatch: fix the usage of capture group ( ... ) 2020-09-09 19:12:37 +02:00
security device_cgroup: Fix RCU list debugging warning 2020-10-01 13:18:13 +02:00
sound ALSA: hda/realtek: Enable front panel headset LED on Lenovo ThinkStation P520 2020-10-01 13:18:22 +02:00
tools objtool: Fix noreturn detection for ignored functions 2020-10-01 13:18:15 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: vgic-its: Fix memory leak on the error path of vgic_add_lpi() 2020-10-01 13:17:56 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.68 2020-09-26 18:03:16 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.