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Josef Bacik 89bca7fe63 btrfs: fix deadlock with fiemap and extent locking 
commit b0ad381fa7 upstream.

While working on the patchset to remove extent locking I got a lockdep
splat with fiemap and pagefaulting with my new extent lock replacement
lock.

This deadlock exists with our normal code, we just don't have lockdep
annotations with the extent locking so we've never noticed it.

Since we're copying the fiemap extent to user space on every iteration
we have the chance of pagefaulting.  Because we hold the extent lock for
the entire range we could mkwrite into a range in the file that we have
mmap'ed.  This would deadlock with the following stack trace

[<0>] lock_extent+0x28d/0x2f0
[<0>] btrfs_page_mkwrite+0x273/0x8a0
[<0>] do_page_mkwrite+0x50/0xb0
[<0>] do_fault+0xc1/0x7b0
[<0>] __handle_mm_fault+0x2fa/0x460
[<0>] handle_mm_fault+0xa4/0x330
[<0>] do_user_addr_fault+0x1f4/0x800
[<0>] exc_page_fault+0x7c/0x1e0
[<0>] asm_exc_page_fault+0x26/0x30
[<0>] rep_movs_alternative+0x33/0x70
[<0>] _copy_to_user+0x49/0x70
[<0>] fiemap_fill_next_extent+0xc8/0x120
[<0>] emit_fiemap_extent+0x4d/0xa0
[<0>] extent_fiemap+0x7f8/0xad0
[<0>] btrfs_fiemap+0x49/0x80
[<0>] __x64_sys_ioctl+0x3e1/0xb50
[<0>] do_syscall_64+0x94/0x1a0
[<0>] entry_SYSCALL_64_after_hwframe+0x6e/0x76

I wrote an fstest to reproduce this deadlock without my replacement lock
and verified that the deadlock exists with our existing locking.

To fix this simply don't take the extent lock for the entire duration of
the fiemap.  This is safe in general because we keep track of where we
are when we're searching the tree, so if an ordered extent updates in
the middle of our fiemap call we'll still emit the correct extents
because we know what offset we were on before.

The only place we maintain the lock is searching delalloc.  Since the
delalloc stuff can change during writeback we want to lock the extent
range so we have a consistent view of delalloc at the time we're
checking to see if we need to set the delalloc flag.

With this patch applied we no longer deadlock with my testcase.

CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-04-03 15:11:42 +02:00
arch x86/efistub: Call mixed mode boot services on the firmware's stack 2024-04-03 15:11:41 +02:00
block Revert "block/mq-deadline: use correct way to throttling write requests" 2024-04-03 15:11:26 +02:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto Revert "crypto: pkcs7 - remove sha1 support" 2024-04-03 15:11:35 +02:00
Documentation docs: Restore "smart quotes" for quotes 2024-04-03 15:11:13 +02:00
drivers wifi: rtw88: 8821cu: Fix connection failure 2024-04-03 15:11:42 +02:00
fs btrfs: fix deadlock with fiemap and extent locking 2024-04-03 15:11:42 +02:00
include mm, vmscan: prevent infinite loop for costly GFP_NOIO | __GFP_RETRY_MAYFAIL allocations 2024-04-03 15:11:40 +02:00
init init/Kconfig: lower GCC version check for -Warray-bounds 2024-04-03 15:11:37 +02:00
io_uring io_uring/waitid: always remove waitid entry for cancel all 2024-04-03 15:11:28 +02:00
ipc Many singleton patches against the MM code. The patch series which are 2023-11-02 19:38:47 -10:00
kernel Fix memory leak in posix_clock_open() 2024-04-03 15:11:42 +02:00
lib pci_iounmap(): Fix MMIO mapping leak 2024-04-03 15:11:07 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm, vmscan: prevent infinite loop for costly GFP_NOIO | __GFP_RETRY_MAYFAIL allocations 2024-04-03 15:11:40 +02:00
net xfrm: Avoid clang fortify warning in copy_to_user_tmpl() 2024-04-03 15:11:36 +02:00
rust rust: Ignore preserve-most functions 2024-01-25 15:45:09 -08:00
samples eventfd: simplify eventfd_signal() 2024-04-03 15:11:23 +02:00
scripts kbuild: Move -Wenum-{compare-conditional,enum-conversion} into W=1 2024-04-03 15:11:22 +02:00
security landlock: Warn once if a Landlock action is requested while disabled 2024-04-03 15:11:19 +02:00
sound ASoC: amd: yc: Revert "Fix non-functional mic on Lenovo 21J2" 2024-04-03 15:11:42 +02:00
tools selftests: mptcp: diag: return KSFT_FAIL not test_cnt 2024-04-03 15:11:36 +02:00
usr arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
virt eventfd: simplify eventfd_signal() 2024-04-03 15:11:23 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: generate kernel.spec in rpmbuild/SPECS/ 2023-10-03 20:49:09 +09:00
.mailmap 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
.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 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
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 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
Makefile Linux 6.7.11 2024-03-26 18:22:50 -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.