[ciqlts8_8] writeback: avoid use-after-free after removing device

[thefossguy-ciq]

• Commit Message Requirements
• Built against Vault/LTS Environment
• kABI Check Passed, where Valid (Pre 9.4 RT does not have kABI stability)
• Boot Test
• Kernel SelfTest results
• Additional Tests as determined relevant

Commit message

jira VULN-6836
cve CVE-2024-0562
commit-author Khazhismel Kumykov <[email protected]> commit f87904c075515f3e1d8f4a7115869d3b914674fd

When a disk is removed, bdi_unregister gets called to stop further writeback and wait for associated delayed work to complete.  However, wb_inode_writeback_end() may schedule bandwidth estimation dwork after this has completed, which can result in the timer attempting to access the just freed bdi_writeback.

Fix this by checking if the bdi_writeback is alive, similar to when scheduling writeback work.

Since this requires wb->work_lock, and wb_inode_writeback_end() may get called from interrupt, switch wb->work_lock to an irqsafe lock.

Link: https://lkml.kernel.org/r/[email protected] Fixes: 45a2966fd641 ("writeback: fix bandwidth estimate for spiky workload")
	Signed-off-by: Khazhismel Kumykov <[email protected]>
	Reviewed-by: Jan Kara <[email protected]>
	Cc: Michael Stapelberg <[email protected]>
	Cc: Wu Fengguang <[email protected]>
	Cc: Alexander Viro <[email protected]>
	Cc: <[email protected]>
	Signed-off-by: Andrew Morton <[email protected]>
(cherry picked from commit f87904c075515f3e1d8f4a7115869d3b914674fd)
	Signed-off-by: Pratham Patel <[email protected]>

Kernel build logs

/run/media/kernel/kernel-src-tree
no .config file found, moving on
[TIMER]{MRPROPER}: 0s
x86_64 architecture detected, copying config
'configs/kernel-4.18.0-x86_64.config' -> '.config'
Setting Local Version for build
CONFIG_LOCALVERSION="-_ppatel__ciqlts8_8-581ac8f566a1"
Making olddefconfig
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/kconfig/conf.o
  YACC    scripts/kconfig/zconf.tab.c
  LEX     scripts/kconfig/zconf.lex.c
  HOSTCC  scripts/kconfig/zconf.tab.o
  HOSTLD  scripts/kconfig/conf
scripts/kconfig/conf  --olddefconfig Kconfig
#
# configuration written to .config
#
Starting Build
scripts/kconfig/conf  --syncconfig Kconfig
  SYSTBL  arch/x86/include/generated/asm/syscalls_32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_32_ia32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_64_x32.h
  SYSTBL  arch/x86/include/generated/asm/syscalls_64.h
  HYPERCALLS arch/x86/include/generated/asm/xen-hypercalls.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_32.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_64.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_x32.h
  WRAP    arch/x86/include/generated/uapi/asm/bpf_perf_event.h
  WRAP    arch/x86/include/generated/uapi/asm/poll.h
  WRAP    arch/x86/include/generated/uapi/asm/socket.h
  UPD     include/config/kernel.release
  UPD     include/generated/uapi/linux/version.h
  DESCEND objtool
  DESCEND bpf/resolve_btfids
[---snip---]
  INSTALL sound/usb/snd-usb-audio.ko
  INSTALL sound/usb/snd-usbmidi-lib.ko
  INSTALL sound/usb/usx2y/snd-usb-us122l.ko
  INSTALL sound/usb/usx2y/snd-usb-usx2y.ko
  INSTALL sound/virtio/virtio_snd.ko
  INSTALL sound/x86/snd-hdmi-lpe-audio.ko
  INSTALL sound/xen/snd_xen_front.ko
  INSTALL virt/lib/irqbypass.ko
  DEPMOD  4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+
[TIMER]{MODULES}: 42s
Making Install
sh ./arch/x86/boot/install.sh 4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+ arch/x86/boot/bzImage \
        System.map "/boot"
[TIMER]{INSTALL}: 10s
Checking kABI
kABI check passed
Setting Default Kernel to /boot/vmlinuz-4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+ and Index to 0
The default is /boot/loader/entries/3d9e347e81244bb1a7c9ccdb05863a3e-4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+.conf with index 0 and kernel /boot/vmlinuz-4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+
The default is /boot/loader/entries/3d9e347e81244bb1a7c9ccdb05863a3e-4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+.conf with index 0 and kernel /boot/vmlinuz-4.18.0-_ppatel__ciqlts8_8-581ac8f566a1+
Generating grub configuration file ...
Adding boot menu entry for EFI firmware configuration
done
Hopefully Grub2.0 took everything ... rebooting after time metrices
[TIMER]{MRPROPER}: 0s
[TIMER]{BUILD}: 1285s
[TIMER]{MODULES}: 42s
[TIMER]{INSTALL}: 10s
[TIMER]{TOTAL} 1342s
Rebooting in 10 seconds

kernel-build.log

Kselftests

$ grep '^ok ' kselftest-before.log | wc -l && grep '^ok ' kselftest-after.log | wc -l
02:08:10|
--------+
230
230

$ grep '^not ok ' kselftest-before.log | wc -l && grep '^not ok ' kselftest-after.log | wc -l
62
62

kselftest-after.log
kselftest-before.log

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