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* [PATCH 6.6 000/111] 6.6.99-rc2 review
@ 2025-07-15 16:37 Greg Kroah-Hartman
  2025-07-15 21:06 ` Miguel Ojeda
                   ` (8 more replies)
  0 siblings, 9 replies; 10+ messages in thread
From: Greg Kroah-Hartman @ 2025-07-15 16:37 UTC (permalink / raw)
  To: stable
  Cc: Greg Kroah-Hartman, patches, linux-kernel, torvalds, akpm, linux,
	shuah, patches, lkft-triage, pavel, jonathanh, f.fainelli,
	sudipm.mukherjee, srw, rwarsow, conor, hargar, broonie, Jann Horn,
	Alexander Viro, Christian Brauner, Jan Kara

This is the start of the stable review cycle for the 6.6.99 release.
There are 111 patches in this series, all will be posted as a response
to this one.  If anyone has any issues with these being applied, please
let me know.

Responses should be made by Thu, 17 Jul 2025 16:35:12 +0000.
Anything received after that time might be too late.

The whole patch series can be found in one patch at:
	https://www.kernel.org/pub/linux/kernel/v6.x/stable-review/patch-6.6.99-rc2.gz
or in the git tree and branch at:
	git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-6.6.y
and the diffstat can be found below.

thanks,

greg k-h

-------------
Pseudo-Shortlog of commits:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Linux 6.6.99-rc2

Michael Jeanson <mjeanson@efficios.com>
    rseq: Fix segfault on registration when rseq_cs is non-zero

Lukas Wunner <lukas@wunner.de>
    crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP()

Namjae Jeon <linkinjeon@kernel.org>
    ksmbd: fix potential use-after-free in oplock/lease break ack

Yeoreum Yun <yeoreum.yun@arm.com>
    kasan: remove kasan_find_vm_area() to prevent possible deadlock

Paulo Alcantara <pc@manguebit.com>
    smb: client: fix potential race in cifs_put_tcon()

Willem de Bruijn <willemb@google.com>
    selftests/bpf: adapt one more case in test_lru_map to the new target_free

Hans de Goede <hdegoede@redhat.com>
    Input: atkbd - do not skip atkbd_deactivate() when skipping ATKBD_CMD_GETID

Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
    HID: quirks: Add quirk for 2 Chicony Electronics HP 5MP Cameras

Zhang Heng <zhangheng@kylinos.cn>
    HID: Add IGNORE quirk for SMARTLINKTECHNOLOGY

Willem de Bruijn <willemb@google.com>
    bpf: Adjust free target to avoid global starvation of LRU map

Nicolas Pitre <npitre@baylibre.com>
    vt: add missing notification when switching back to text mode

Filipe Manana <fdmanana@suse.com>
    btrfs: fix assertion when building free space tree

Long Li <longli@microsoft.com>
    net: mana: Record doorbell physical address in PF mode

Akira Inoue <niyarium@gmail.com>
    HID: lenovo: Add support for ThinkPad X1 Tablet Thin Keyboard Gen2

Xiaowei Li <xiaowei.li@simcom.com>
    net: usb: qmi_wwan: add SIMCom 8230C composition

Yasmin Fitzgerald <sunoflife1.git@gmail.com>
    ALSA: hda/realtek - Enable mute LED on HP Pavilion Laptop 15-eg100

Yuzuru10 <yuzuru_10@proton.me>
    ASoC: amd: yc: add quirk for Acer Nitro ANV15-41 internal mic

Fengnan Chang <changfengnan@bytedance.com>
    io_uring: make fallocate be hashed work

Tiwei Bie <tiwei.btw@antgroup.com>
    um: vector: Reduce stack usage in vector_eth_configure()

Thomas Fourier <fourier.thomas@gmail.com>
    atm: idt77252: Add missing `dma_map_error()`

Ronnie Sahlberg <rsahlberg@whamcloud.com>
    ublk: sanity check add_dev input for underflow

Somnath Kotur <somnath.kotur@broadcom.com>
    bnxt_en: Set DMA unmap len correctly for XDP_REDIRECT

Shravya KN <shravya.k-n@broadcom.com>
    bnxt_en: Fix DCB ETS validation

Alok Tiwari <alok.a.tiwari@oracle.com>
    net: ll_temac: Fix missing tx_pending check in ethtools_set_ringparam()

Sean Nyekjaer <sean@geanix.com>
    can: m_can: m_can_handle_lost_msg(): downgrade msg lost in rx message to debug level

Oleksij Rempel <o.rempel@pengutronix.de>
    net: phy: microchip: limit 100M workaround to link-down events on LAN88xx

Mingming Cao <mmc@linux.ibm.com>
    ibmvnic: Fix hardcoded NUM_RX_STATS/NUM_TX_STATS with dynamic sizeof

Kito Xu <veritas501@foxmail.com>
    net: appletalk: Fix device refcount leak in atrtr_create()

Eric Dumazet <edumazet@google.com>
    netfilter: flowtable: account for Ethernet header in nf_flow_pppoe_proto()

Zheng Qixing <zhengqixing@huawei.com>
    nbd: fix uaf in nbd_genl_connect() error path

Nigel Croxon <ncroxon@redhat.com>
    raid10: cleanup memleak at raid10_make_request

Wang Jinchao <wangjinchao600@gmail.com>
    md/raid1: Fix stack memory use after return in raid1_reshape

Mikko Perttunen <mperttunen@nvidia.com>
    drm/tegra: nvdec: Fix dma_alloc_coherent error check

Daniil Dulov <d.dulov@aladdin.ru>
    wifi: zd1211rw: Fix potential NULL pointer dereference in zd_mac_tx_to_dev()

Shyam Prasad N <sprasad@microsoft.com>
    cifs: all initializations for tcon should happen in tcon_info_alloc

Paulo Alcantara <pc@manguebit.com>
    smb: client: fix DFS interlink failover

Paulo Alcantara <pc@manguebit.com>
    smb: client: avoid unnecessary reconnects when refreshing referrals

Kuen-Han Tsai <khtsai@google.com>
    usb: dwc3: Abort suspend on soft disconnect failure

Pawel Laszczak <pawell@cadence.com>
    usb: cdnsp: Fix issue with CV Bad Descriptor test

Lee Jones <lee@kernel.org>
    usb: cdnsp: Replace snprintf() with the safer scnprintf() variant

Pawel Laszczak <pawell@cadence.com>
    usb:cdnsp: remove TRB_FLUSH_ENDPOINT command

Filipe Manana <fdmanana@suse.com>
    btrfs: fix inode lookup error handling during log replay

Filipe Manana <fdmanana@suse.com>
    btrfs: return a btrfs_inode from btrfs_iget_logging()

Filipe Manana <fdmanana@suse.com>
    btrfs: remove redundant root argument from fixup_inode_link_count()

Filipe Manana <fdmanana@suse.com>
    btrfs: remove redundant root argument from btrfs_update_inode_fallback()

Filipe Manana <fdmanana@suse.com>
    btrfs: remove noinline from btrfs_update_inode()

Jakub Kicinski <kuba@kernel.org>
    netlink: make sure we allow at least one dump skb

Kuniyuki Iwashima <kuniyu@google.com>
    netlink: Fix rmem check in netlink_broadcast_deliver().

Chao Yu <chao@kernel.org>
    erofs: fix to add missing tracepoint in erofs_read_folio()

Al Viro <viro@zeniv.linux.org.uk>
    ksmbd: fix a mount write count leak in ksmbd_vfs_kern_path_locked()

Stefan Metzmacher <metze@samba.org>
    smb: server: make use of rdma_destroy_qp()

Jann Horn <jannh@google.com>
    x86/mm: Disable hugetlb page table sharing on 32-bit

Mikhail Paulyshka <me@mixaill.net>
    x86/rdrand: Disable RDSEED on AMD Cyan Skillfish

Uwe Kleine-König <u.kleine-koenig@baylibre.com>
    pwm: mediatek: Ensure to disable clocks in error path

Alexander Gordeev <agordeev@linux.ibm.com>
    mm/vmalloc: leave lazy MMU mode on PTE mapping error

Florian Fainelli <florian.fainelli@broadcom.com>
    scripts/gdb: fix interrupts.py after maple tree conversion

Florian Fainelli <florian.fainelli@broadcom.com>
    scripts/gdb: de-reference per-CPU MCE interrupts

Florian Fainelli <florian.fainelli@broadcom.com>
    scripts/gdb: fix interrupts display after MCP on x86

Baolin Wang <baolin.wang@linux.alibaba.com>
    mm: fix the inaccurate memory statistics issue for users

Wei Yang <richard.weiyang@gmail.com>
    maple_tree: fix mt_destroy_walk() on root leaf node

Achill Gilgenast <fossdd@pwned.life>
    kallsyms: fix build without execinfo

Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Revert "ACPI: battery: negate current when discharging"

Thomas Zimmermann <tzimmermann@suse.de>
    drm/framebuffer: Acquire internal references on GEM handles

Kuen-Han Tsai <khtsai@google.com>
    Revert "usb: gadget: u_serial: Add null pointer check in gs_start_io"

Kuen-Han Tsai <khtsai@google.com>
    usb: gadget: u_serial: Fix race condition in TTY wakeup

Simona Vetter <simona.vetter@ffwll.ch>
    drm/gem: Fix race in drm_gem_handle_create_tail()

Christian König <christian.koenig@amd.com>
    drm/ttm: fix error handling in ttm_buffer_object_transfer

Matthew Brost <matthew.brost@intel.com>
    drm/sched: Increment job count before swapping tail spsc queue

Thomas Zimmermann <tzimmermann@suse.de>
    drm/gem: Acquire references on GEM handles for framebuffers

Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
    wifi: prevent A-MSDU attacks in mesh networks

Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
    pinctrl: qcom: msm: mark certain pins as invalid for interrupts

Håkon Bugge <haakon.bugge@oracle.com>
    md/md-bitmap: fix GPF in bitmap_get_stats()

Guillaume Nault <gnault@redhat.com>
    gre: Fix IPv6 multicast route creation.

Sean Christopherson <seanjc@google.com>
    KVM: SVM: Reject SEV{-ES} intra host migration if vCPU creation is in-flight

David Woodhouse <dwmw@amazon.co.uk>
    KVM: x86/xen: Allow 'out of range' event channel ports in IRQ routing table.

JP Kobryn <inwardvessel@gmail.com>
    x86/mce: Make sure CMCI banks are cleared during shutdown on Intel

Yazen Ghannam <yazen.ghannam@amd.com>
    x86/mce: Don't remove sysfs if thresholding sysfs init fails

Yazen Ghannam <yazen.ghannam@amd.com>
    x86/mce/amd: Fix threshold limit reset

Yazen Ghannam <yazen.ghannam@amd.com>
    x86/mce/amd: Add default names for MCA banks and blocks

Dan Carpenter <dan.carpenter@linaro.org>
    ipmi:msghandler: Fix potential memory corruption in ipmi_create_user()

David Howells <dhowells@redhat.com>
    rxrpc: Fix oops due to non-existence of prealloc backlog struct

Christian Eggers <ceggers@arri.de>
    Bluetooth: HCI: Set extended advertising data synchronously

Leo Yan <leo.yan@arm.com>
    perf: build: Setup PKG_CONFIG_LIBDIR for cross compilation

Liam R. Howlett <Liam.Howlett@oracle.com>
    maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate()

David Howells <dhowells@redhat.com>
    rxrpc: Fix bug due to prealloc collision

Victor Nogueira <victor@mojatatu.com>
    net/sched: Abort __tc_modify_qdisc if parent class does not exist

Yue Haibing <yuehaibing@huawei.com>
    atm: clip: Fix NULL pointer dereference in vcc_sendmsg()

Kuniyuki Iwashima <kuniyu@google.com>
    atm: clip: Fix infinite recursive call of clip_push().

Kuniyuki Iwashima <kuniyu@google.com>
    atm: clip: Fix memory leak of struct clip_vcc.

Kuniyuki Iwashima <kuniyu@google.com>
    atm: clip: Fix potential null-ptr-deref in to_atmarpd().

Oleksij Rempel <o.rempel@pengutronix.de>
    net: phy: smsc: Fix link failure in forced mode with Auto-MDIX

Oleksij Rempel <o.rempel@pengutronix.de>
    net: phy: smsc: Force predictable MDI-X state on LAN87xx

Oleksij Rempel <o.rempel@pengutronix.de>
    net: phy: smsc: Fix Auto-MDIX configuration when disabled by strap

EricChan <chenchuangyu@xiaomi.com>
    net: stmmac: Fix interrupt handling for level-triggered mode in DWC_XGMAC2

Michal Luczaj <mhal@rbox.co>
    vsock: Fix IOCTL_VM_SOCKETS_GET_LOCAL_CID to check also `transport_local`

Michal Luczaj <mhal@rbox.co>
    vsock: Fix transport_* TOCTOU

Michal Luczaj <mhal@rbox.co>
    vsock: Fix transport_{g2h,h2g} TOCTOU

Jiayuan Chen <jiayuan.chen@linux.dev>
    tcp: Correct signedness in skb remaining space calculation

Kuniyuki Iwashima <kuniyu@google.com>
    tipc: Fix use-after-free in tipc_conn_close().

Stefano Garzarella <sgarzare@redhat.com>
    vsock: fix `vsock_proto` declaration

Kuniyuki Iwashima <kuniyu@google.com>
    netlink: Fix wraparounds of sk->sk_rmem_alloc.

Al Viro <viro@zeniv.linux.org.uk>
    fix proc_sys_compare() handling of in-lookup dentries

Mario Limonciello <mario.limonciello@amd.com>
    pinctrl: amd: Clear GPIO debounce for suspend

Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
    Bluetooth: hci_event: Fix not marking Broadcast Sink BIS as connected

Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
    Bluetooth: hci_sync: Fix not disabling advertising instance

Richard Fitzgerald <rf@opensource.cirrus.com>
    ASoC: cs35l56: probe() should fail if the device ID is not recognized

Peter Zijlstra <peterz@infradead.org>
    perf: Revert to requiring CAP_SYS_ADMIN for uprobes

Luo Gengkun <luogengkun@huaweicloud.com>
    perf/core: Fix the WARN_ON_ONCE is out of lock protected region

Shengjiu Wang <shengjiu.wang@nxp.com>
    ASoC: fsl_asrc: use internal measured ratio for non-ideal ratio mode

Kaustabh Chakraborty <kauschluss@disroot.org>
    drm/exynos: exynos7_drm_decon: add vblank check in IRQ handling

Linus Torvalds <torvalds@linux-foundation.org>
    eventpoll: don't decrement ep refcount while still holding the ep mutex


-------------

Diffstat:

 Documentation/bpf/map_hash.rst                     |   8 +-
 Documentation/bpf/map_lru_hash_update.dot          |   6 +-
 Makefile                                           |   4 +-
 arch/um/drivers/vector_kern.c                      |  42 +--
 arch/x86/Kconfig                                   |   2 +-
 arch/x86/include/asm/msr-index.h                   |   1 +
 arch/x86/kernel/cpu/amd.c                          |   7 +
 arch/x86/kernel/cpu/mce/amd.c                      |  28 +-
 arch/x86/kernel/cpu/mce/core.c                     |   8 +-
 arch/x86/kernel/cpu/mce/intel.c                    |   1 +
 arch/x86/kvm/svm/sev.c                             |   4 +
 arch/x86/kvm/xen.c                                 |  15 +-
 crypto/ecc.c                                       |   2 +-
 drivers/acpi/battery.c                             |  19 +-
 drivers/atm/idt77252.c                             |   5 +
 drivers/block/nbd.c                                |   6 +-
 drivers/block/ublk_drv.c                           |   3 +-
 drivers/char/ipmi/ipmi_msghandler.c                |   3 +-
 drivers/gpu/drm/drm_framebuffer.c                  |  31 +-
 drivers/gpu/drm/drm_gem.c                          |  74 ++++-
 drivers/gpu/drm/drm_internal.h                     |   2 +
 drivers/gpu/drm/exynos/exynos7_drm_decon.c         |   4 +
 drivers/gpu/drm/tegra/nvdec.c                      |   6 +-
 drivers/gpu/drm/ttm/ttm_bo_util.c                  |  13 +-
 drivers/hid/hid-ids.h                              |   6 +
 drivers/hid/hid-lenovo.c                           |   8 +
 drivers/hid/hid-multitouch.c                       |   8 +-
 drivers/hid/hid-quirks.c                           |   3 +
 drivers/input/keyboard/atkbd.c                     |   3 +-
 drivers/md/md-bitmap.c                             |   3 +-
 drivers/md/raid1.c                                 |   1 +
 drivers/md/raid10.c                                |  10 +-
 drivers/net/can/m_can/m_can.c                      |   2 +-
 drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c      |   2 +
 drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c      |   2 +-
 drivers/net/ethernet/ibm/ibmvnic.h                 |   8 +-
 drivers/net/ethernet/microsoft/mana/gdma_main.c    |   3 +
 drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c |  24 +-
 drivers/net/ethernet/xilinx/ll_temac_main.c        |   2 +-
 drivers/net/phy/microchip.c                        |   2 +-
 drivers/net/phy/smsc.c                             |  57 +++-
 drivers/net/usb/qmi_wwan.c                         |   1 +
 drivers/net/wireless/zydas/zd1211rw/zd_mac.c       |   6 +-
 drivers/pinctrl/pinctrl-amd.c                      |  11 +
 drivers/pinctrl/qcom/pinctrl-msm.c                 |  20 ++
 drivers/pwm/pwm-mediatek.c                         |  13 +-
 drivers/tty/vt/vt.c                                |   1 +
 drivers/usb/cdns3/cdnsp-debug.h                    | 358 ++++++++++-----------
 drivers/usb/cdns3/cdnsp-ep0.c                      |  18 +-
 drivers/usb/cdns3/cdnsp-gadget.c                   |   6 +-
 drivers/usb/cdns3/cdnsp-gadget.h                   |  11 +-
 drivers/usb/cdns3/cdnsp-ring.c                     |  27 +-
 drivers/usb/dwc3/core.c                            |   9 +-
 drivers/usb/dwc3/gadget.c                          |  22 +-
 drivers/usb/gadget/function/u_serial.c             |  12 +-
 fs/btrfs/btrfs_inode.h                             |   2 +-
 fs/btrfs/free-space-tree.c                         |  16 +-
 fs/btrfs/inode.c                                   |  18 +-
 fs/btrfs/transaction.c                             |   2 +-
 fs/btrfs/tree-log.c                                | 331 +++++++++++--------
 fs/erofs/data.c                                    |   2 +
 fs/eventpoll.c                                     |  12 +-
 fs/proc/inode.c                                    |   2 +-
 fs/proc/proc_sysctl.c                              |  18 +-
 fs/proc/task_mmu.c                                 |  14 +-
 fs/smb/client/cifsglob.h                           |   3 +
 fs/smb/client/cifsproto.h                          |  13 +-
 fs/smb/client/connect.c                            |  47 ++-
 fs/smb/client/dfs.c                                |  73 ++---
 fs/smb/client/dfs.h                                |  42 ++-
 fs/smb/client/dfs_cache.c                          | 198 +++++++-----
 fs/smb/client/fs_context.h                         |   1 +
 fs/smb/client/misc.c                               |   9 +
 fs/smb/client/namespace.c                          |   2 +-
 fs/smb/server/smb2pdu.c                            |  29 +-
 fs/smb/server/transport_rdma.c                     |   5 +-
 fs/smb/server/vfs.c                                |   1 +
 include/drm/drm_file.h                             |   3 +
 include/drm/drm_framebuffer.h                      |   7 +
 include/drm/spsc_queue.h                           |   4 +-
 include/linux/math.h                               |  12 +
 include/linux/mm.h                                 |   5 +
 include/net/af_vsock.h                             |   2 +-
 include/net/netfilter/nf_flow_table.h              |   2 +-
 io_uring/opdef.c                                   |   1 +
 kernel/bpf/bpf_lru_list.c                          |   9 +-
 kernel/bpf/bpf_lru_list.h                          |   1 +
 kernel/events/core.c                               |   6 +-
 kernel/rseq.c                                      |  60 +++-
 lib/maple_tree.c                                   |  14 +-
 mm/kasan/report.c                                  |  13 +-
 mm/vmalloc.c                                       |  22 +-
 net/appletalk/ddp.c                                |   1 +
 net/atm/clip.c                                     |  64 +++-
 net/bluetooth/hci_event.c                          |  39 +--
 net/bluetooth/hci_sync.c                           | 215 ++++++++-----
 net/ipv4/tcp.c                                     |   2 +-
 net/ipv6/addrconf.c                                |   9 +-
 net/netlink/af_netlink.c                           |  90 +++---
 net/rxrpc/call_accept.c                            |   4 +
 net/sched/sch_api.c                                |  23 +-
 net/tipc/topsrv.c                                  |   2 +
 net/vmw_vsock/af_vsock.c                           |  57 +++-
 net/wireless/util.c                                |  52 ++-
 scripts/gdb/linux/constants.py.in                  |   7 +
 scripts/gdb/linux/interrupts.py                    |  16 +-
 scripts/gdb/linux/mapletree.py                     | 252 +++++++++++++++
 scripts/gdb/linux/xarray.py                        |  28 ++
 sound/pci/hda/patch_realtek.c                      |   1 +
 sound/soc/amd/yc/acp6x-mach.c                      |   7 +
 sound/soc/codecs/cs35l56-shared.c                  |   2 +-
 sound/soc/fsl/fsl_asrc.c                           |   3 +-
 tools/arch/x86/include/asm/msr-index.h             |   1 +
 tools/build/feature/Makefile                       |  25 +-
 tools/include/linux/kallsyms.h                     |   4 +
 tools/perf/Makefile.perf                           |  27 +-
 tools/testing/selftests/bpf/test_lru_map.c         | 105 +++---
 117 files changed, 1948 insertions(+), 1042 deletions(-)


From gregkh@linuxfoundation.org Tue Jul 15 18:35:42 2025
Message-ID: <20250715163542.121531643@linuxfoundation.org>
User-Agent: quilt/0.68
Date: Tue, 15 Jul 2025 18:35:43 +0200
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: patches@lists.linux.dev, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, linux@roeck-us.net, shuah@kernel.org, patches@kernelci.org, lkft-triage@lists.linaro.org, pavel@denx.de, jonathanh@nvidia.com, f.fainelli@gmail.com, sudipm.mukherjee@gmail.com, srw@sladewatkins.net, rwarsow@gmx.de, conor@kernel.org, hargar@microsoft.com, broonie@kernel.org,
 Jann Horn <jannh@google.com>,
 Alexander Viro <viro@zeniv.linux.org.uk>,
 Christian Brauner <brauner@kernel.org>,
 Jan Kara <jack@suse.cz>,
 Linus Torvalds <torvalds@linux-foundation.org>
X-stable: review
X-Patchwork-Hint: ignore
Subject: [PATCH 6.6 001/111] eventpoll: dont decrement ep refcount while still holding the ep mutex
MIME-Version: 1.0

6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@linux-foundation.org>

commit 8c2e52ebbe885c7eeaabd3b7ddcdc1246fc400d2 upstream.

Jann Horn points out that epoll is decrementing the ep refcount and then
doing a

    mutex_unlock(&ep->mtx);

afterwards. That's very wrong, because it can lead to a use-after-free.

That pattern is actually fine for the very last reference, because the
code in question will delay the actual call to "ep_free(ep)" until after
it has unlocked the mutex.

But it's wrong for the much subtler "next to last" case when somebody
*else* may also be dropping their reference and free the ep while we're
still using the mutex.

Note that this is true even if that other user is also using the same ep
mutex: mutexes, unlike spinlocks, can not be used for object ownership,
even if they guarantee mutual exclusion.

A mutex "unlock" operation is not atomic, and as one user is still
accessing the mutex as part of unlocking it, another user can come in
and get the now released mutex and free the data structure while the
first user is still cleaning up.

See our mutex documentation in Documentation/locking/mutex-design.rst,
in particular the section [1] about semantics:

	"mutex_unlock() may access the mutex structure even after it has
	 internally released the lock already - so it's not safe for
	 another context to acquire the mutex and assume that the
	 mutex_unlock() context is not using the structure anymore"

So if we drop our ep ref before the mutex unlock, but we weren't the
last one, we may then unlock the mutex, another user comes in, drops
_their_ reference and releases the 'ep' as it now has no users - all
while the mutex_unlock() is still accessing it.

Fix this by simply moving the ep refcount dropping to outside the mutex:
the refcount itself is atomic, and doesn't need mutex protection (that's
the whole _point_ of refcounts: unlike mutexes, they are inherently
about object lifetimes).

Reported-by: Jann Horn <jannh@google.com>
Link: https://docs.kernel.org/locking/mutex-design.html#semantics [1]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/eventpoll.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -772,7 +772,7 @@ static bool __ep_remove(struct eventpoll
 	call_rcu(&epi->rcu, epi_rcu_free);
 
 	percpu_counter_dec(&ep->user->epoll_watches);
-	return ep_refcount_dec_and_test(ep);
+	return true;
 }
 
 /*
@@ -780,14 +780,14 @@ static bool __ep_remove(struct eventpoll
  */
 static void ep_remove_safe(struct eventpoll *ep, struct epitem *epi)
 {
-	WARN_ON_ONCE(__ep_remove(ep, epi, false));
+	if (__ep_remove(ep, epi, false))
+		WARN_ON_ONCE(ep_refcount_dec_and_test(ep));
 }
 
 static void ep_clear_and_put(struct eventpoll *ep)
 {
 	struct rb_node *rbp, *next;
 	struct epitem *epi;
-	bool dispose;
 
 	/* We need to release all tasks waiting for these file */
 	if (waitqueue_active(&ep->poll_wait))
@@ -820,10 +820,8 @@ static void ep_clear_and_put(struct even
 		cond_resched();
 	}
 
-	dispose = ep_refcount_dec_and_test(ep);
 	mutex_unlock(&ep->mtx);
-
-	if (dispose)
+	if (ep_refcount_dec_and_test(ep))
 		ep_free(ep);
 }
 
@@ -1003,7 +1001,7 @@ again:
 		dispose = __ep_remove(ep, epi, true);
 		mutex_unlock(&ep->mtx);
 
-		if (dispose)
+		if (dispose && ep_refcount_dec_and_test(ep))
 			ep_free(ep);
 		goto again;
 	}



^ permalink raw reply	[flat|nested] 10+ messages in thread
end of thread, other threads:[~2025-07-17  9:04 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-07-15 16:37 [PATCH 6.6 000/111] 6.6.99-rc2 review Greg Kroah-Hartman
2025-07-15 21:06 ` Miguel Ojeda
2025-07-16  9:22 ` Harshit Mogalapalli
2025-07-16 10:16 ` Jon Hunter
2025-07-16 10:40 ` Mark Brown
2025-07-16 11:07 ` Ron Economos
2025-07-16 11:44 ` Naresh Kamboju
2025-07-16 15:16 ` Peter Schneider
2025-07-16 18:45 ` Florian Fainelli
2025-07-17  9:03 ` Brett A C Sheffield

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