linux-stable.git/include, branch linux-6.12.y

kcov: fix data corruption and race conditions on PREEMPT_RT

2026-08-27T12:32:05+00:00

commit 2eed77fdcb0cc48e8eccb2bcd4b7f2c6d650e84c upstream.

syzbot is reporting KCOV state corruption on PREEMPT_RT kernels, for the
temporary storage used for saving/restoring remote KCOV state is currently
allocated as the per-CPU area.

On PREEMPT_RT kernels, softirq handlers run as preemptible task threads
(e.g., ksoftirqd). If a softirq context preempts a task running a remote
KCOV session, it safely saves the task's state into the per-CPU area.
However, if that softirq thread is subsequently preempted by a higher-
priority softirq thread on the same CPU, the second softirq will overwrite
the same per-CPU area, permanently destroying the original task's KCOV
state.

Fix this data corruption by moving the temporary storage from the per-CPU
area to the per-thread area. Since each softirq thread now owns its own
task context, nested softirq preemption no longer causes data overwrites.

Note that while the temporary storage is now on a per-thread basis, the
per-CPU kcov_percpu_data.lock must be retained, for we need to ensure that
kcov_remote_start() and kcov_remote_stop() operate atomically without
racing against asynchronous interrupts that manipulate the current task's
KCOV state.

It is likely that GFP_KERNEL allocation by vmalloc_node() in kcov_init()
has already called panic() before returning NULL, for there will be no
OOM-killable userspace processes when __init function of built-in module
runs. But this patch also fixes crashing the kernel when vmalloc_node()
in kcov_init() returned NULL, for kcov_init() left per-CPU irq_area == NULL
but kcov_remote_start() depends on per-CPU irq_area != NULL, resulting in

  (1) doing vmalloc() in kcov_remote_start() despite !in_task() context

  (2) out-of-array-bounds access if (1) succeeded but
      kcov->remote_size < CONFIG_KCOV_IRQ_AREA_SIZE

  (3) always leak memory allocated by (1), eventually killing all
      OOM-killable userspace processes

problems.

Link: https://lore.kernel.org/43552d09-2ce2-4b19-b0d3-a2d1ab952145@I-love.SAKURA.ne.jp
Reported-by: syzbot+3f51ad7ac3ae57a6fdcc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3f51ad7ac3ae57a6fdcc
Reported-by: syzbot+47cf95ca1f9dcca872c8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=47cf95ca1f9dcca872c8
Reported-by: syzbot+8a173e13208949931dc7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8a173e13208949931dc7
Reported-by: syzbot+90984d3713722683112e@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=90984d3713722683112e
Analyzed-by: AI Mode in Google Search (no mail address)
Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts")
Signed-off-by: Tetsuo Handa 
Reviewed-by: Alexander Potapenko 
Cc: Alan Stern 
Cc: Andrey Konovalov 
Cc: Christoph Hellwig 
Cc: Clark Williams 
Cc: Dmitry Vyukov 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Mark Brown 
Cc: Roman Gushchin 
Cc: Sebastian Andrzej Siewior 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

inet: frags: change inet_frag_kill() to defer refcount updates

2026-08-27T12:32:04+00:00

[ Upstream commit eb0dfc0ef195a04e519b15d73cf25d8c25ee8df7 ]

In the following patch, we no longer assume inet_frag_kill()
callers own a reference.

Consuming two refcounts from inet_frag_kill() would lead in UAF.

Propagate the pointer to the refs that will be consumed later
by the final inet_frag_putn() call.

Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20250312082250.1803501-4-edumazet@google.com
Signed-off-by: Paolo Abeni 
Stable-dep-of: 653d7ddf6cba ("inet: frags: publish queues before arming timer")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

inet: frags: add inet_frag_putn() helper

2026-08-27T12:32:04+00:00

[ Upstream commit ae2d90355aa5592b0e99c8bbb4c3fa1d8e205f1b ]

inet_frag_putn() can release multiple references
in one step.

Use it in inet_frags_free_cb().

Replace inet_frag_put(X) with inet_frag_putn(X, 1)

Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20250312082250.1803501-2-edumazet@google.com
Signed-off-by: Paolo Abeni 
Stable-dep-of: 653d7ddf6cba ("inet: frags: publish queues before arming timer")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()

2026-08-27T12:32:04+00:00

commit dbe556972100fabb8e5a1b3d2163831ff07b1e8e upstream.

netfs_unlock_abandoned_read_pages(rreq) accesses the index of the folios it
is wanting to unlock and compares that to rreq->no_unlock_folio so that it
doesn't unlock a folio being read for netfs_perform_write() or
netfs_write_begin().

However, given that netfs_unlock_abandoned_read_pages() is called _after_
NETFS_RREQ_IN_PROGRESS is cleared, the one folio that it's not allowed to
dereference is the one specified by ->no_unlock_folio as ownership
immediately reverts to the caller.

Fix this by storing the folio pointer instead and using that rather than
the index.  Also fix netfs_unlock_read_folio() where the same applies.

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells 
Link: https://patch.msgid.link/20260512123404.719402-20-dhowells@redhat.com
cc: Paulo Alcantara 
cc: Viacheslav Dubeyko 
cc: Matthew Wilcox 
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner 
Signed-off-by: Shishkin Aleksey 
Signed-off-by: Greg Kroah-Hartman

PCI: host-generic: Fix NULL pointer dereference on 32-bit CAM systems

2026-08-27T12:32:03+00:00

commit 008cb88edb41f3c7c8e0ed763ff9f26719830984 upstream.

On 32-bit systems the config space is too large to ioremap in one go, so
pci_ecam_create() maps each bus segment separately and relies on the
->add_bus callback (pci_ecam_add_bus) to populate the per-bus mapping in
cfg->winp[]. pci_ecam_map_bus() then uses that mapping as the base for
every config access.

The generic ECAM ops (pci_generic_ecam_ops) already provide the ->add_bus
and ->remove_bus callbacks, but the CAM (legacy) ops in pci-host-generic.c
do not. As a result, on a 32-bit host using "pci-host-cam-generic" the
per-bus mapping is never set up and the first config read dereferences a
NULL base, crashing during bus enumeration:

 Unable to handle kernel NULL pointer dereference at virtual address 00000800
 Oops [#1]
 CPU: 0 PID: 1 Comm: swapper Not tainted 6.9.7+ #43
 Hardware name: Digilent Nexys-Video-A7 RV32 (DT)
 epc : pci_generic_config_read+0x40/0xb0
  ra : pci_generic_config_read+0x2c/0xb0
 [] pci_generic_config_read+0x40/0xb0
 [] pci_bus_read_config_dword+0x50/0xb0
 [] pci_bus_generic_read_dev_vendor_id+0x3c/0x1ec
 [] pci_scan_single_device+0xa4/0x11c
 [] pci_scan_slot+0x9c/0x23c
 [] pci_scan_child_bus_extend+0x58/0x2f4
 [] pci_scan_root_bus_bridge+0x64/0xe8
 [] pci_host_probe+0x20/0xc8
 [] pci_host_common_probe+0x144/0x1e4

Fix this by giving the CAM ops the same ->add_bus/->remove_bus callbacks.
Since pci_ecam_add_bus() and pci_ecam_remove_bus() are static to ecam.c,
move the CAM ops definition there as pci_generic_cam_ops (mirroring
pci_generic_ecam_ops) and export it for pci-host-generic.c to reference.

Fixes: 8fe55ef23387 ("PCI: Dynamically map ECAM regions")
Signed-off-by: Steffen Persvold 
[mani: removed timestamp from log]
Signed-off-by: Manivannan Sadhasivam 
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260709122446.3151899-1-spersvold@gmail.com
Signed-off-by: Greg Kroah-Hartman

ip_tunnel: adapt iptunnel_xmit_stats() to NETDEV_PCPU_STAT_DSTATS

2026-08-23T12:22:51+00:00

commit 8431c602f551549f082bbfa67f3003f2d8e3e132 upstream.

Blamed commits forgot that vxlan/geneve use udp_tunnel[6]_xmit_skb() which
call iptunnel_xmit_stats().

iptunnel_xmit_stats() was assuming tunnels were only using
NETDEV_PCPU_STAT_TSTATS.

@syncp offset in pcpu_sw_netstats and pcpu_dstats is different.

32bit kernels would either have corruptions or freezes if the syncp
sequence was overwritten.

This patch also moves pcpu_stat_type closer to dev->{t,d}stats to avoid
a potential cache line miss since iptunnel_xmit_stats() needs to read it.

Fixes: 6fa6de302246 ("geneve: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Fixes: be226352e8dc ("vxlan: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Signed-off-by: Eric Dumazet 
Reviewed-by: Guillaume Nault 
Link: https://patch.msgid.link/20260311123110.1471930-1-edumazet@google.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: harmonize tstats and dstats

2026-08-23T12:22:51+00:00

commit d3ed6dee73c560fad0a8e152c8e233b3fb3a2e44 upstream.

After the blamed commits below, some UDP tunnel use dstats for
accounting. On the xmit path, all the UDP-base tunnels ends up
using iptunnel_xmit_stats() for stats accounting, and the latter
assumes the relevant (tunnel) network device uses tstats.

The end result is some 'funny' stat report for the mentioned UDP
tunnel, e.g. when no packet is actually dropped and a bunch of
packets are transmitted:

gnv2:  mtu 1450 qdisc noqueue \
		state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether ee:7d:09:87:90:ea brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
         14916      23      0      15       0       0
    TX:  bytes packets errors dropped carrier collsns
             0    1566      0       0       0       0

Address the issue ensuring the same binary layout for the overlapping
fields of dstats and tstats. While this solution is a bit hackish, is
smaller and with no performance pitfall compared to other alternatives
i.e. supporting both dstat and tstat in iptunnel_xmit_stats() or
reverting the blamed commit.

With time we should possibly move all the IP-based tunnel (and virtual
devices) to dstats.

Fixes: c77200c07491 ("bareudp: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Fixes: 6fa6de302246 ("geneve: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Fixes: be226352e8dc ("vxlan: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Signed-off-by: Paolo Abeni 
Reviewed-by: Guillaume Nault 
Link: https://patch.msgid.link/2e1c444cf0f63ae472baff29862c4c869be17031.1738432804.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

mm/pagewalk: split walk_page_range_novma() into kernel/user parts

2026-08-23T12:22:48+00:00

[ Upstream commit 96d81e4766f9e88b66a0502b5a7f34a4c20ac754 ]

walk_page_range_novma() is rather confusing - it supports two modes, one
used often, the other used only for debugging.

The first mode is the common case of traversal of kernel page tables,
which is what nearly all callers use this for.

Secondly it provides an unusual debugging interface that allows for the
traversal of page tables in a userland range of memory even for that
memory which is not described by a VMA.

It is far from certain that such page tables should even exist, but
perhaps this is precisely why it is useful as a debugging mechanism.

As a result, this is utilised by ptdump only.  Historically, things were
reversed - ptdump was the only user, and other parts of the kernel evolved
to use the kernel page table walking here.

Since we have some complicated and confusing locking rules for the novma
case, it makes sense to separate the two usages into their own functions.

Doing this also provide self-documentation as to the intent of the caller
- are they doing something rather unusual or are they simply doing a
standard kernel page table walk?

We therefore establish two separate functions - walk_page_range_debug()
for this single usage, and walk_kernel_page_table_range() for general
kernel page table walking.

The walk_page_range_debug() function is currently used to traverse both
userland and kernel mappings, so we maintain this and in the case of
kernel mappings being traversed, we have walk_page_range_debug() invoke
walk_kernel_page_table_range() internally.

We additionally make walk_page_range_debug() internal to mm.

Link: https://lkml.kernel.org/r/20250605135104.90720-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes 
Acked-by: Mike Rapoport (Microsoft) 
Acked-by: Qi Zheng 
Reviewed-by: Oscar Salvador 
Reviewed-by: Suren Baghdasaryan 
Reviewed-by: Vlastimil Babka 
Acked-by: David Hildenbrand 
Cc: Albert Ou 
Cc: Alexandre Ghiti 
Cc: Barry Song 
Cc: Huacai Chen 
Cc: Jann Horn 
Cc: Jonas Bonn 
Cc: Liam Howlett 
Cc: Michal Hocko 
Cc: Muchun Song 
Cc: Palmer Dabbelt 
Cc: Paul Walmsley 
Cc: Stafford Horne 
Cc: Stefan Kristiansson 
Cc: WANG Xuerui 
Signed-off-by: Andrew Morton 
Stable-dep-of: 27c32e553834 ("mm/ptdump: always stabilise against page table freeing using init_mm")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

include/linux/fs.h: add inode_lock_killable()

2026-08-23T12:22:47+00:00

[ Upstream commit d8c5507cd140d9471472ece673e70250b957c595 ]

Prepare for making inode operations killable while they're waiting for
the lock.

Signed-off-by: Max Kellermann 
Link: https://lore.kernel.org/20250513150327.1373061-1-max.kellermann@ionos.com
Signed-off-by: Christian Brauner 
Stable-dep-of: fa724e235cfd ("cifs: add fscache_resize_cookie() to cifs_setsize()")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

vrf: Make pcpu_dstats update functions available to other modules.

2026-08-23T12:22:47+00:00

[ Upstream commit 18eabadd73ae60023ab05e376246bd725fb0c113 ]

Currently vrf is the only module that uses NETDEV_PCPU_STAT_DSTATS.
In order to make this kind of statistics available to other modules,
we need to define the update functions in netdevice.h.

Therefore, let's define dev_dstats_*() functions for RX and TX packet
updates (packets, bytes and drops). Use these new functions in vrf.c
instead of vrf_rx_stats() and the other manual counter updates.

While there, update the type of the "len" variables to "unsigned int",
so that there're aligned with both skb->len and the new dstats update
functions.

Signed-off-by: Guillaume Nault 
Link: https://patch.msgid.link/d7a552ee382c79f4854e7fcc224cf176cd21150d.1733313925.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski 
Stable-dep-of: b9553558b48d ("vxlan: use pskb_network_may_pull() for transmit path header pulls")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman