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Rafael Aquini 54abe19e00 writeback: fix dereferencing NULL mapping->host on writeback_page_template 
When commit 19343b5bdd ("mm/page-writeback: introduce tracepoint for
wait_on_page_writeback()") repurposed the writeback_dirty_page trace event
as a template to create its new wait_on_page_writeback trace event, it
ended up opening a window to NULL pointer dereference crashes due to the
(infrequent) occurrence of a race where an access to a page in the
swap-cache happens concurrently with the moment this page is being written
to disk and the tracepoint is enabled:

    BUG: kernel NULL pointer dereference, address: 0000000000000040
    #PF: supervisor read access in kernel mode
    #PF: error_code(0x0000) - not-present page
    PGD 800000010ec0a067 P4D 800000010ec0a067 PUD 102353067 PMD 0
    Oops: 0000 [#1] PREEMPT SMP PTI
    CPU: 1 PID: 1320 Comm: shmem-worker Kdump: loaded Not tainted 6.4.0-rc5+ #13
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230301gitf80f052277c8-1.fc37 03/01/2023
    RIP: 0010:trace_event_raw_event_writeback_folio_template+0x76/0xf0
    Code: 4d 85 e4 74 5c 49 8b 3c 24 e8 06 98 ee ff 48 89 c7 e8 9e 8b ee ff ba 20 00 00 00 48 89 ef 48 89 c6 e8 fe d4 1a 00 49 8b 04 24 <48> 8b 40 40 48 89 43 28 49 8b 45 20 48 89 e7 48 89 43 30 e8 a2 4d
    RSP: 0000:ffffaad580b6fb60 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: ffff90e38035c01c RCX: 0000000000000000
    RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff90e38035c044
    RBP: ffff90e38035c024 R08: 0000000000000002 R09: 0000000000000006
    R10: ffff90e38035c02e R11: 0000000000000020 R12: ffff90e380bac000
    R13: ffffe3a7456d9200 R14: 0000000000001b81 R15: ffffe3a7456d9200
    FS:  00007f2e4e8a15c0(0000) GS:ffff90e3fbc80000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000000040 CR3: 00000001150c6003 CR4: 0000000000170ee0
    Call Trace:
     <TASK>
     ? __die+0x20/0x70
     ? page_fault_oops+0x76/0x170
     ? kernelmode_fixup_or_oops+0x84/0x110
     ? exc_page_fault+0x65/0x150
     ? asm_exc_page_fault+0x22/0x30
     ? trace_event_raw_event_writeback_folio_template+0x76/0xf0
     folio_wait_writeback+0x6b/0x80
     shmem_swapin_folio+0x24a/0x500
     ? filemap_get_entry+0xe3/0x140
     shmem_get_folio_gfp+0x36e/0x7c0
     ? find_busiest_group+0x43/0x1a0
     shmem_fault+0x76/0x2a0
     ? __update_load_avg_cfs_rq+0x281/0x2f0
     __do_fault+0x33/0x130
     do_read_fault+0x118/0x160
     do_pte_missing+0x1ed/0x2a0
     __handle_mm_fault+0x566/0x630
     handle_mm_fault+0x91/0x210
     do_user_addr_fault+0x22c/0x740
     exc_page_fault+0x65/0x150
     asm_exc_page_fault+0x22/0x30

This problem arises from the fact that the repurposed writeback_dirty_page
trace event code was written assuming that every pointer to mapping
(struct address_space) would come from a file-mapped page-cache object,
thus mapping->host would always be populated, and that was a valid case
before commit 19343b5bdd.  The swap-cache address space
(swapper_spaces), however, doesn't populate its ->host (struct inode)
pointer, thus leading to the crashes in the corner-case aforementioned.

commit 19343b5bdd ended up breaking the assignment of __entry->name and
__entry->ino for the wait_on_page_writeback tracepoint -- both dependent
on mapping->host carrying a pointer to a valid inode.  The assignment of
__entry->name was fixed by commit 68f23b8906 ("memcg: fix a crash in
wb_workfn when a device disappears"), and this commit fixes the remaining
case, for __entry->ino.

Link: https://lkml.kernel.org/r/20230606233613.1290819-1-aquini@redhat.com
Fixes: 19343b5bdd ("mm/page-writeback: introduce tracepoint for wait_on_page_writeback()")
Signed-off-by: Rafael Aquini <aquini@redhat.com>
Reviewed-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-06-19 13:19:31 -07:00
arch riscv/purgatory: remove PGO flags 2023-06-12 11:31:51 -07:00
block block: make bio_check_eod work for zero sized devices 2023-05-24 08:19:26 -06:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto This push fixes the following problems: 2023-05-07 10:57:14 -07:00
Documentation Tracing fixes: 2023-05-29 07:20:13 -04:00
drivers phy fixes for 6.4 2023-05-28 20:05:07 -04:00
fs ocfs2: check new file size on fallocate call 2023-06-12 11:31:52 -07:00
include writeback: fix dereferencing NULL mapping->host on writeback_page_template 2023-06-19 13:19:31 -07:00
init Objtool changes for v6.4: 2023-04-28 14:02:54 -07:00
io_uring io_uring: unlock sqd->lock before sq thread release CPU 2023-05-25 09:30:13 -06:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel kexec: support purgatories with .text.hot sections 2023-06-12 11:31:50 -07:00
lib lib/test_vmalloc.c: avoid garbage in page array 2023-06-12 11:31:51 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm zswap: do not shrink if cgroup may not zswap 2023-06-12 11:31:52 -07:00
net Networking fixes for 6.4-rc4, including fixes from bluetooth and bpf 2023-05-25 10:55:26 -07:00
rust Rust changes for v6.4 2023-04-30 11:20:22 -07:00
samples samples/bpf: Drop unnecessary fallthrough 2023-05-16 19:44:05 +02:00
scripts Locking changes in v6.4: 2023-05-05 12:56:55 -07:00
security integrity-v6.4 2023-04-29 10:11:32 -07:00
sound ALSA: hda/realtek: Enable headset onLenovo M70/M90 2023-05-24 14:18:59 +02:00
tools radix-tree: move declarations to header 2023-06-12 11:31:50 -07:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt KVM: Fix vcpu_array[0] races 2023-05-19 13:56:26 -04:00
.clang-format cxl for v6.4 2023-04-30 11:51:51 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore linux-kselftest-kunit-6.4-rc1 2023-04-24 12:31:32 -07:00
.mailmap mailmap: add entry for John Keeping 2023-06-12 11:31:52 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: sctp: move Neil to CREDITS 2023-05-12 08:51:32 +01:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS ARM: SoC fixes for 6.4 2023-05-26 16:17:56 -07:00
Makefile Linux 6.4-rc4 2023-05-28 07:49:00 -04:00
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.