Re: [syzbot] [ocfs2?] KMSAN: uninit-value in _find_next_bit

[syzbot <syzbot+7ea0b96c4ddb49fd1a70@syzkaller.appspotmail.com>]

Hello,

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

failed to copy syz-execprog to VM: scp failed: timedout after 1m0s ["scp" "-P" "22" "-F" "/dev/null" "-o" "UserKnownHostsFile=/dev/null" "-o" "IdentitiesOnly=yes" "-o" "BatchMode=yes" "-o" "StrictHostKeyChecking=no" "-o" "ConnectTimeout=10" "-v" "/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/bin/linux_amd64/syz-execprog" "root@10.128.1.184:./syz-execprog"]
Executing: program /usr/bin/ssh host 10.128.1.184, user root, command sftp
debug1: OpenSSH_10.0p2 Debian-7, OpenSSL 3.5.4 30 Sep 2025
debug1: Reading configuration data /dev/null
debug1: Connecting to 10.128.1.184 [10.128.1.184] port 22.
debug1: fd 3 clearing O_NONBLOCK
debug1: Connection established.
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa_sk type -1
debug1: identity file /root/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: identity file /root/.ssh/id_ed25519_sk type -1
debug1: identity file /root/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /root/.ssh/id_xmss type -1
debug1: identity file /root/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_10.0p2 Debian-7
debug1: Remote protocol version 2.0, remote software version OpenSSH_9.9
debug1: compat_banner: match: OpenSSH_9.9 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 10.128.1.184:22 as 'root'
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: mlkem768x25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:EAvWV3GG8odMD+k20F251zjwXNDbyLo/P7N2oY0DvFQ
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
Warning: Permanently added '10.128.1.184' (ED25519) to the list of known hosts.
debug1: ssh_packet_send2_wrapped: resetting send seqnr 3
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: Sending SSH2_MSG_EXT_INFO
debug1: expecting SSH2_MSG_NEWKEYS
debug1: ssh_packet_read_poll2: resetting read seqnr 3
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_ext_info_client_parse: server-sig-algs=<ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ssh-ed25519@openssh.com,sk-ecdsa-sha2-nistp256@openssh.com,rsa-sha2-512,rsa-sha2-256>
debug1: kex_ext_info_check_ver: publickey-hostbound@openssh.com=<0>
debug1: kex_ext_info_check_ver: ping@openssh.com=<0>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_ext_info_client_parse: server-sig-algs=<ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ssh-ed25519@openssh.com,sk-ecdsa-sha2-nistp256@openssh.com,rsa-sha2-512,rsa-sha2-256>
Authenticated to 10.128.1.184 ([10.128.1.184]:22) using "none".
debug1: channel 0: new session [client-session] (inactive timeout: 0)
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Sending subsystem: sftp
debug1: pledge: fork




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-build509210889=/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='go1.26.0'
GOWORK=''
PKG_CONFIG='pkg-config'

git status (err=<nil>)
HEAD detached at 1a086e7c78
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=1a086e7c785fa4decf3678c4237591fa6fad1621 -X github.com/google/syzkaller/prog.gitRevisionDate=20260413-125522"  ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1a086e7c785fa4decf3678c4237591fa6fad1621 -X github.com/google/syzkaller/prog.gitRevisionDate=20260413-125522"  ./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=1a086e7c785fa4decf3678c4237591fa6fad1621 -X github.com/google/syzkaller/prog.gitRevisionDate=20260413-125522"  -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=\"1a086e7c785fa4decf3678c4237591fa6fad1621\"
/usr/bin/ld: /tmp/cc0Ro39l.o: in function `Connection::Connect(char const*, char const*)':
executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x386): 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



Tested on:

commit:         59bd5ae0 Merge tag 'for-v7.1' of git://git.kernel.org/..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
kernel config:  https://syzkaller.appspot.com/x/.config?x=dd34a4e3f8a96df8
dashboard link: https://syzkaller.appspot.com/bug?extid=7ea0b96c4ddb49fd1a70
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11819a6a580000