Message-ID: <695dc296.050a0220.1c677c.0352.GAE@google.com>
Date: Tue, 06 Jan 2026 18:19:02 -0800
From: syzbot <syzbot+b4444e3c972a7a124187@...kaller.appspotmail.com>
To: chao@...nel.org, jaegeuk@...nel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [f2fs?] KASAN: use-after-free Read in f2fs_write_end_io (2)

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

c 0x1003 length: 249 > 9
[   99.252780][ T4680] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[   99.258304][ T4680] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[   99.262003][ T4680] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[   99.904250][  T947] wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[   99.908039][  T947] wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
[   99.960090][ T1131] wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[   99.963625][ T1131] wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
[  101.111055][ T5380] chnl_net:caif_netlink_parms(): no params data found
[  101.277872][ T5380] bridge0: port 1(bridge_slave_0) entered blocking state
[  101.286086][ T5380] bridge0: port 1(bridge_slave_0) entered disabled state
[  101.289331][ T5380] bridge_slave_0: entered allmulticast mode
[  101.304573][ T5380] bridge_slave_0: entered promiscuous mode
[  101.311175][ T5380] bridge0: port 2(bridge_slave_1) entered blocking state
[  101.314400][ T5380] bridge0: port 2(bridge_slave_1) entered disabled state
[  101.318351][ T5380] bridge_slave_1: entered allmulticast mode
[  101.322134][ T5380] bridge_slave_1: entered promiscuous mode
[  101.348427][ T5380] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[  101.357433][ T5380] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[  101.383478][ T5380] team0: Port device team_slave_0 added
[  101.388135][ T5380] team0: Port device team_slave_1 added
[  101.411977][ T5380] batman_adv: batadv0: Adding interface: batadv_slave_0
[  101.415073][ T5380] batman_adv: batadv0: The MTU of interface batadv_slave_0 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[  101.427067][ T5380] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
[  101.433759][ T5380] batman_adv: batadv0: Adding interface: batadv_slave_1
[  101.437187][ T5380] batman_adv: batadv0: The MTU of interface batadv_slave_1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[  101.448054][ T5380] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
[  101.483243][ T5380] hsr_slave_0: entered promiscuous mode
[  101.486999][ T5380] hsr_slave_1: entered promiscuous mode
[  101.640469][ T5380] netdevsim netdevsim0 netdevsim0: renamed from eth0
[  101.650511][ T5380] netdevsim netdevsim0 netdevsim1: renamed from eth1
[  101.657246][ T5380] netdevsim netdevsim0 netdevsim2: renamed from eth2
[  101.663682][ T5380] netdevsim netdevsim0 netdevsim3: renamed from eth3
[  101.742774][ T5380] 8021q: adding VLAN 0 to HW filter on device bond0
[  101.761501][ T5380] 8021q: adding VLAN 0 to HW filter on device team0
[  101.770624][  T947] bridge0: port 1(bridge_slave_0) entered blocking state
[  101.773903][  T947] bridge0: port 1(bridge_slave_0) entered forwarding state
[  101.786737][ T1131] bridge0: port 2(bridge_slave_1) entered blocking state
[  101.789882][ T1131] bridge0: port 2(bridge_slave_1) entered forwarding state
[  102.002757][ T5380] 8021q: adding VLAN 0 to HW filter on device batadv0
[  102.041139][ T5380] veth0_vlan: entered promiscuous mode
[  102.050273][ T5380] veth1_vlan: entered promiscuous mode
[  102.080200][ T5380] veth0_macvtap: entered promiscuous mode
[  102.087176][ T5380] veth1_macvtap: entered promiscuous mode
[  102.108084][ T5380] batman_adv: batadv0: Interface activated: batadv_slave_0
[  102.119233][ T5380] batman_adv: batadv0: Interface activated: batadv_slave_1
[  102.129583][  T947] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
[  102.141577][  T947] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
[  102.145405][  T947] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
[  102.160213][ T4047] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
[  102.423332][ T3019] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  102.589933][ T3019] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  102.698091][ T3019] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  102.788477][ T3019] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  105.309210][ T3019] bridge_slave_1: left allmulticast mode
[  105.311909][ T3019] bridge_slave_1: left promiscuous mode
[  105.331282][ T3019] bridge0: port 2(bridge_slave_1) entered disabled state
[  105.387138][ T3019] bridge_slave_0: left allmulticast mode
[  105.389688][ T3019] bridge_slave_0: left promiscuous mode
[  105.392386][ T3019] bridge0: port 1(bridge_slave_0) entered disabled state
[  106.096537][ T3019] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[  106.103033][ T3019] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[  106.117388][ T3019] bond0 (unregistering): Released all slaves
[  106.229126][ T3019] hsr_slave_0: left promiscuous mode
[  106.246123][ T3019] hsr_slave_1: left promiscuous mode
[  106.258491][ T3019] batman_adv: batadv0: Interface deactivated: batadv_slave_0
[  106.261745][ T3019] batman_adv: batadv0: Removing interface: batadv_slave_0
[  106.286794][ T3019] batman_adv: batadv0: Interface deactivated: batadv_slave_1
[  106.290111][ T3019] batman_adv: batadv0: Removing interface: batadv_slave_1
[  106.325813][ T3019] veth1_macvtap: left promiscuous mode
[  106.329044][ T3019] veth0_macvtap: left promiscuous mode
[  106.331694][ T3019] veth1_vlan: left promiscuous mode
[  106.334122][ T3019] veth0_vlan: left promiscuous mode
[  106.797480][ T3019] team0 (unregistering): Port device team_slave_1 removed
[  106.821140][ T3019] team0 (unregistering): Port device team_slave_0 removed
2026/01/07 02:18:07 executed programs: 0
[  108.259947][   T46] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
[  108.264618][   T46] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
[  108.270695][   T46] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[  108.274422][   T46] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[  108.278195][   T46] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[  108.730010][ T5451] chnl_net:caif_netlink_parms(): no params data found
[  108.907477][ T5451] bridge0: port 1(bridge_slave_0) entered blocking state
[  108.910655][ T5451] bridge0: port 1(bridge_slave_0) entered disabled state
[  108.913831][ T5451] bridge_slave_0: entered allmulticast mode
[  108.929157][ T5451] bridge_slave_0: entered promiscuous mode
[  108.939210][ T5451] bridge0: port 2(bridge_slave_1) entered blocking state
[  108.942482][ T5451] bridge0: port 2(bridge_slave_1) entered disabled state
[  108.950846][ T5451] bridge_slave_1: entered allmulticast mode
[  108.965783][ T5451] bridge_slave_1: entered promiscuous mode
[  109.018144][ T5451] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[  109.026049][ T5451] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[  109.073929][ T5451] team0: Port device team_slave_0 added
[  109.085217][ T5451] team0: Port device team_slave_1 added
[  109.128253][ T5451] batman_adv: batadv0: Adding interface: batadv_slave_0
[  109.131303][ T5451] batman_adv: batadv0: The MTU of interface batadv_slave_0 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[  109.156217][ T5451] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
[  109.177176][ T5451] batman_adv: batadv0: Adding interface: batadv_slave_1
[  109.180214][ T5451] batman_adv: batadv0: The MTU of interface batadv_slave_1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1532 would solve the problem.
[  109.208335][ T5451] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
[  109.278165][ T5451] hsr_slave_0: entered promiscuous mode
[  109.286205][ T5451] hsr_slave_1: entered promiscuous mode
[  109.779620][ T5451] netdevsim netdevsim0 netdevsim0: renamed from eth0
[  109.800234][ T5451] netdevsim netdevsim0 netdevsim1: renamed from eth1
[  109.807679][ T5451] netdevsim netdevsim0 netdevsim2: renamed from eth2
[  109.829275][ T5451] netdevsim netdevsim0 netdevsim3: renamed from eth3
[  109.967755][ T5451] 8021q: adding VLAN 0 to HW filter on device bond0
[  109.993637][ T5451] 8021q: adding VLAN 0 to HW filter on device team0
[  110.013449][  T947] bridge0: port 1(bridge_slave_0) entered blocking state
[  110.016837][  T947] bridge0: port 1(bridge_slave_0) entered forwarding state
[  110.041939][  T947] bridge0: port 2(bridge_slave_1) entered blocking state
[  110.045001][  T947] bridge0: port 2(bridge_slave_1) entered forwarding state
[  110.113140][ T5451] hsr0: Slave A (hsr_slave_0) is not up; please bring it up to get a fully working HSR network
[  110.126403][ T5451] hsr0: Slave B (hsr_slave_1) is not up; please bring it up to get a fully working HSR network
[  110.306727][   T46] Bluetooth: hci0: command tx timeout
[  110.407891][ T5451] 8021q: adding VLAN 0 to HW filter on device batadv0
[  110.474914][ T5451] veth0_vlan: entered promiscuous mode
[  110.501129][ T5451] veth1_vlan: entered promiscuous mode
[  110.548766][ T5451] veth0_macvtap: entered promiscuous mode
[  110.566415][ T5451] veth1_macvtap: entered promiscuous mode
[  110.594368][ T5451] batman_adv: batadv0: Interface activated: batadv_slave_0
[  110.627391][ T5451] batman_adv: batadv0: Interface activated: batadv_slave_1
[  110.639617][  T947] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
[  110.643516][  T947] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
[  110.667089][  T947] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
[  110.702519][  T947] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
[  110.791338][  T947] wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[  110.795044][  T947] wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
[  110.848266][  T947] wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[  110.851713][  T947] wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
SYZFAIL: failed to recv rpc
fd=3 want=4 recv=0 n=0 (errno 9: Bad file descriptor)
[  112.188996][ T1131] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  113.352275][ T1131] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  113.627013][ T1131] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  113.684954][ T1131] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  113.807220][ T1131] bridge_slave_1: left allmulticast mode
[  113.809850][ T1131] bridge_slave_1: left promiscuous mode
[  113.812539][ T1131] bridge0: port 2(bridge_slave_1) entered disabled state
[  113.832063][ T1131] bridge_slave_0: left allmulticast mode
[  113.834590][ T1131] bridge_slave_0: left promiscuous mode
[  113.837572][ T1131] bridge0: port 1(bridge_slave_0) entered disabled state
[  114.221189][ T1131] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[  114.227289][ T1131] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[  114.232468][ T1131] bond0 (unregistering): Released all slaves
[  114.487951][ T1131] hsr_slave_0: left promiscuous mode
[  114.490767][ T1131] hsr_slave_1: left promiscuous mode
[  114.498999][ T1131] batman_adv: batadv0: Interface deactivated: batadv_slave_0
[  114.502267][ T1131] batman_adv: batadv0: Removing interface: batadv_slave_0
[  114.517714][ T1131] batman_adv: batadv0: Interface deactivated: batadv_slave_1
[  114.521062][ T1131] batman_adv: batadv0: Removing interface: batadv_slave_1
[  114.549206][ T1131] veth1_macvtap: left promiscuous mode
[  114.551802][ T1131] veth0_macvtap: left promiscuous mode
[  114.554336][ T1131] veth1_vlan: left promiscuous mode
[  114.567501][ T1131] veth0_vlan: left promiscuous mode
[  114.940636][ T1131] team0 (unregistering): Port device team_slave_1 removed
[  114.967019][ T1131] team0 (unregistering): Port device team_slave_0 removed


syzkaller build log:
go env (err=<nil>)
AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE='auto'
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/syzkaller/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/syzkaller/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1445029477=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/go.mod'
GOMODCACHE='/syzkaller/jobs/linux/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/syzkaller/jobs/linux/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/syzkaller/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.24.4'
GOWORK=''
PKG_CONFIG='pkg-config'

git status (err=<nil>)
HEAD detached at d1b870e1003b
nothing to commit, working tree clean


tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
go list -f '{{.Stale}}' -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=d1b870e1003b52891d2196c1e2ee42fe905010ba -X github.com/google/syzkaller/prog.gitRevisionDate=20251128-125159"  ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=d1b870e1003b52891d2196c1e2ee42fe905010ba -X github.com/google/syzkaller/prog.gitRevisionDate=20251128-125159"  ./sys/syz-sysgen
make .descriptions
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
bin/syz-sysgen
touch .descriptions
GOOS=linux GOARCH=amd64 go build -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=d1b870e1003b52891d2196c1e2ee42fe905010ba -X github.com/google/syzkaller/prog.gitRevisionDate=20251128-125159"  -o ./bin/linux_amd64/syz-execprog github.com/google/syzkaller/tools/syz-execprog
mkdir -p ./bin/linux_amd64
g++ -o ./bin/linux_amd64/syz-executor executor/executor.cc \
	-m64 -O2 -pthread -Wall -Werror -Wparentheses -Wunused-const-variable -Wframe-larger-than=16384 -Wno-stringop-overflow -Wno-array-bounds -Wno-format-overflow -Wno-unused-but-set-variable -Wno-unused-command-line-argument -static-pie -std=c++17 -I. -Iexecutor/_include   -DGOOS_linux=1 -DGOARCH_amd64=1 \
	-DHOSTGOOS_linux=1 -DGIT_REVISION=\"d1b870e1003b52891d2196c1e2ee42fe905010ba\"
/usr/bin/ld: /tmp/cc4kC0pD.o: in function `Connection::Connect(char const*, char const*)':
executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x104): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
./tools/check-syzos.sh 2>/dev/null


Error text is too large and was truncated, full error text is at:
https://syzkaller.appspot.com/x/error.txt?x=12df7e9a580000


Tested on:

commit:         af98ee9d f2fs: fix use-after-free in f2fs_write_end_io
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/syzbot
kernel config:  https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
dashboard link: https://syzkaller.appspot.com/bug?extid=b4444e3c972a7a124187
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.

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