Message-ID: <695e2fcd.050a0220.1c677c.035e.GAE@google.com>
Date: Wed, 07 Jan 2026 02:05:01 -0800
From: syzbot <syzbot+b4444e3c972a7a124187@...kaller.appspotmail.com>
To: chao@...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:

50:50:50
[   96.324372][ T4608] wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
[   96.383532][   T13] wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[   96.388909][   T13] wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
[   98.981820][ T4685] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
[   98.986155][ T4685] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
[   98.989980][ T4685] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[   98.993960][ T4685] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[   98.997492][ T4685] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[  101.080148][ T5400] chnl_net:caif_netlink_parms(): no params data found
[  101.260660][ T5400] bridge0: port 1(bridge_slave_0) entered blocking state
[  101.271979][ T5400] bridge0: port 1(bridge_slave_0) entered disabled state
[  101.275128][ T5400] bridge_slave_0: entered allmulticast mode
[  101.291786][ T5400] bridge_slave_0: entered promiscuous mode
[  101.298693][ T5400] bridge0: port 2(bridge_slave_1) entered blocking state
[  101.309121][ T5400] bridge0: port 2(bridge_slave_1) entered disabled state
[  101.312608][ T5400] bridge_slave_1: entered allmulticast mode
[  101.321527][ T5400] bridge_slave_1: entered promiscuous mode
[  101.374348][ T5400] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[  101.394422][ T5400] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[  101.443124][ T5400] team0: Port device team_slave_0 added
[  101.452091][ T5400] team0: Port device team_slave_1 added
[  101.495794][ T5400] batman_adv: batadv0: Adding interface: batadv_slave_0
[  101.498939][ T5400] 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.
[  101.541327][ T5400] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
[  101.571912][ T5400] batman_adv: batadv0: Adding interface: batadv_slave_1
[  101.574976][ T5400] 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.
[  101.611346][ T5400] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
[  101.716466][ T5400] hsr_slave_0: entered promiscuous mode
[  101.720143][ T5400] hsr_slave_1: entered promiscuous mode
[  102.035333][ T5400] netdevsim netdevsim0 netdevsim0: renamed from eth0
[  102.057801][ T5400] netdevsim netdevsim0 netdevsim1: renamed from eth1
[  102.066664][ T5400] netdevsim netdevsim0 netdevsim2: renamed from eth2
[  102.085706][ T5400] netdevsim netdevsim0 netdevsim3: renamed from eth3
[  102.225047][ T5400] 8021q: adding VLAN 0 to HW filter on device bond0
[  102.254868][ T5400] 8021q: adding VLAN 0 to HW filter on device team0
[  102.295073][ T1127] bridge0: port 1(bridge_slave_0) entered blocking state
[  102.298513][ T1127] bridge0: port 1(bridge_slave_0) entered forwarding state
[  102.313626][ T1127] bridge0: port 2(bridge_slave_1) entered blocking state
[  102.316779][ T1127] bridge0: port 2(bridge_slave_1) entered forwarding state
[  102.538955][ T5400] 8021q: adding VLAN 0 to HW filter on device batadv0
[  102.576951][ T5400] veth0_vlan: entered promiscuous mode
[  102.584258][ T5400] veth1_vlan: entered promiscuous mode
[  102.606836][ T5400] veth0_macvtap: entered promiscuous mode
[  102.617483][ T5400] veth1_macvtap: entered promiscuous mode
[  102.631115][ T5400] batman_adv: batadv0: Interface activated: batadv_slave_0
[  102.644037][ T5400] batman_adv: batadv0: Interface activated: batadv_slave_1
[  102.656266][ T4637] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
[  102.667017][ T4637] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
[  102.678832][ T4637] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
[  102.699431][ T4637] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
[  102.827338][ T4637] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  102.874563][ T4637] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  102.916861][ T4637] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  102.955081][ T4637] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
2026/01/07 10:04:23 executed programs: 0
[  103.704543][   T47] Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
[  103.708655][   T47] Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
[  103.713035][   T47] Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
[  103.716711][   T47] Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
[  103.720706][   T47] Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
[  103.874928][ T5441] chnl_net:caif_netlink_parms(): no params data found
[  104.002432][ T5441] bridge0: port 1(bridge_slave_0) entered blocking state
[  104.005631][ T5441] bridge0: port 1(bridge_slave_0) entered disabled state
[  104.009058][ T5441] bridge_slave_0: entered allmulticast mode
[  104.025056][ T5441] bridge_slave_0: entered promiscuous mode
[  104.033625][ T5441] bridge0: port 2(bridge_slave_1) entered blocking state
[  104.037020][ T5441] bridge0: port 2(bridge_slave_1) entered disabled state
[  104.040130][ T5441] bridge_slave_1: entered allmulticast mode
[  104.053666][ T5441] bridge_slave_1: entered promiscuous mode
[  104.115026][ T5441] bond0: (slave bond_slave_0): Enslaving as an active interface with an up link
[  104.136512][ T5441] bond0: (slave bond_slave_1): Enslaving as an active interface with an up link
[  104.178539][ T5441] team0: Port device team_slave_0 added
[  104.183425][ T5441] team0: Port device team_slave_1 added
[  104.207708][ T5441] batman_adv: batadv0: Adding interface: batadv_slave_0
[  104.210805][ T5441] 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.
[  104.223299][ T5441] batman_adv: batadv0: Not using interface batadv_slave_0 (retrying later): interface not active
[  104.230664][ T5441] batman_adv: batadv0: Adding interface: batadv_slave_1
[  104.234253][ T5441] 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.
[  104.246544][ T5441] batman_adv: batadv0: Not using interface batadv_slave_1 (retrying later): interface not active
[  104.281972][ T5441] hsr_slave_0: entered promiscuous mode
[  104.285329][ T5441] hsr_slave_1: entered promiscuous mode
[  104.288328][ T5441] debugfs: 'hsr0' already exists in 'hsr'
[  104.290838][ T5441] Cannot create hsr debugfs directory
[  105.062924][ T4637] bridge_slave_1: left allmulticast mode
[  105.065283][ T4637] bridge_slave_1: left promiscuous mode
[  105.072635][ T4637] bridge0: port 2(bridge_slave_1) entered disabled state
[  105.084121][ T4637] bridge_slave_0: left allmulticast mode
[  105.086616][ T4637] bridge_slave_0: left promiscuous mode
[  105.089229][ T4637] bridge0: port 1(bridge_slave_0) entered disabled state
[  105.434250][ T4637] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[  105.441979][ T4637] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[  105.446733][ T4637] bond0 (unregistering): Released all slaves
[  105.546762][ T4637] hsr_slave_0: left promiscuous mode
[  105.561587][ T4637] hsr_slave_1: left promiscuous mode
[  105.564672][ T4637] batman_adv: batadv0: Interface deactivated: batadv_slave_0
[  105.568054][ T4637] batman_adv: batadv0: Removing interface: batadv_slave_0
[  105.578013][ T4637] batman_adv: batadv0: Interface deactivated: batadv_slave_1
[  105.581111][ T4637] batman_adv: batadv0: Removing interface: batadv_slave_1
[  105.608041][ T4637] veth1_macvtap: left promiscuous mode
[  105.610648][ T4637] veth0_macvtap: left promiscuous mode
[  105.628271][ T4637] veth1_vlan: left promiscuous mode
[  105.632462][ T4637] veth0_vlan: left promiscuous mode
[  105.736315][   T47] Bluetooth: hci0: command tx timeout
[  106.107211][ T4637] team0 (unregistering): Port device team_slave_1 removed
[  106.134290][ T4637] team0 (unregistering): Port device team_slave_0 removed
[  106.578691][ T5441] netdevsim netdevsim0 netdevsim0: renamed from eth0
[  106.599515][ T5441] netdevsim netdevsim0 netdevsim1: renamed from eth1
[  106.616734][ T5441] netdevsim netdevsim0 netdevsim2: renamed from eth2
[  106.630262][ T5441] netdevsim netdevsim0 netdevsim3: renamed from eth3
[  107.173027][ T5441] 8021q: adding VLAN 0 to HW filter on device bond0
[  107.206957][ T5441] 8021q: adding VLAN 0 to HW filter on device team0
[  107.255745][ T3440] bridge0: port 1(bridge_slave_0) entered blocking state
[  107.259102][ T3440] bridge0: port 1(bridge_slave_0) entered forwarding state
[  107.305836][ T3440] bridge0: port 2(bridge_slave_1) entered blocking state
[  107.309126][ T3440] bridge0: port 2(bridge_slave_1) entered forwarding state
[  107.468490][ T5441] 8021q: adding VLAN 0 to HW filter on device batadv0
[  107.504820][ T5441] veth0_vlan: entered promiscuous mode
[  107.513636][ T5441] veth1_vlan: entered promiscuous mode
[  107.533127][ T5441] veth0_macvtap: entered promiscuous mode
[  107.538225][ T5441] veth1_macvtap: entered promiscuous mode
[  107.551007][ T5441] batman_adv: batadv0: Interface activated: batadv_slave_0
[  107.563537][ T5441] batman_adv: batadv0: Interface activated: batadv_slave_1
[  107.573370][   T13] netdevsim netdevsim0 netdevsim0: set [1, 0] type 2 family 0 port 6081 - 0
[  107.583446][   T13] netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
[  107.587551][   T13] netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
[  107.620236][   T13] netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
[  107.687153][ T3440] wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[  107.690521][ T3440] wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
[  107.739992][   T13] wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
[  107.744091][   T13] wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
[  107.821622][   T47] Bluetooth: hci0: command tx timeout
SYZFAIL: failed to recv rpc
fd=3 want=4 recv=0 n=0 (errno 9: Bad file descriptor)
[  109.064804][ T3440] netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  110.112799][ T3440] netdevsim netdevsim0 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  110.530922][ T3440] netdevsim netdevsim0 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  110.573006][ T3440] netdevsim netdevsim0 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
[  110.696901][ T3440] bridge_slave_1: left allmulticast mode
[  110.699371][ T3440] bridge_slave_1: left promiscuous mode
[  110.712675][ T3440] bridge0: port 2(bridge_slave_1) entered disabled state
[  110.717544][ T3440] bridge_slave_0: left allmulticast mode
[  110.720008][ T3440] bridge_slave_0: left promiscuous mode
[  110.724098][ T3440] bridge0: port 1(bridge_slave_0) entered disabled state
[  111.067299][ T3440] bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
[  111.073241][ T3440] bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
[  111.077962][ T3440] bond0 (unregistering): Released all slaves
[  111.288410][ T3440] hsr_slave_0: left promiscuous mode
[  111.290938][ T3440] hsr_slave_1: left promiscuous mode
[  111.302397][ T3440] batman_adv: batadv0: Interface deactivated: batadv_slave_0
[  111.305777][ T3440] batman_adv: batadv0: Removing interface: batadv_slave_0
[  111.326508][ T3440] batman_adv: batadv0: Interface deactivated: batadv_slave_1
[  111.329929][ T3440] batman_adv: batadv0: Removing interface: batadv_slave_1
[  111.348723][ T3440] veth1_macvtap: left promiscuous mode
[  111.362446][ T3440] veth0_macvtap: left promiscuous mode
[  111.365101][ T3440] veth1_vlan: left promiscuous mode
[  111.367513][ T3440] veth0_vlan: left promiscuous mode
[  111.699085][ T3440] team0 (unregistering): Port device team_slave_1 removed
[  111.720608][ T3440] 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-build1275535676=/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/cc4qdZbn.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=15dbee9a580000


Tested on:

commit:         1860d530 f2fs: fix to avoid UAF 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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