[syzbot] [nilfs?] WARNING in nilfs_btree_mark

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f0caa1d49cc0 Merge tag 'hid-for-linus-2026031701' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12d868da580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d46eab0cfd31c214
dashboard link: https://syzkaller.appspot.com/bug?extid=98a040252119df0506f8
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1452974a580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-f0caa1d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/790e2ce16030/vmlinux-f0caa1d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dcb6a5644f0c/bzImage-f0caa1d4.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/93d9925377df/mount_1.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98a040...@syzkaller.appspotmail.com

------------[ cut here ]------------
ret == -ENOENT
WARNING: fs/nilfs2/btree.c:2356 at nilfs_btree_mark+0x1c9/0x210 fs/nilfs2/btree.c:2356, CPU#0: syz.0.17/5469
Modules linked in:
CPU: 0 UID: 0 PID: 5469 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:nilfs_btree_mark+0x1c9/0x210 fs/nilfs2/btree.c:2356
Code: 48 8b 05 4a f8 6e 0f 48 3b 44 24 10 75 26 89 e8 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 88 f8 17 fe 90 <0f> 0b 90 bd fe ff ff ff eb c3 e8 58 99 02 08 44 89 f1 80 e1 07 80
RSP: 0018:ffffc90003d375b0 EFLAGS: 00010293
RAX: ffffffff83adb7f8 RBX: ffff888042014000 RCX: ffff888040904980
RDX: 0000000000000000 RSI: 00000000fffffffe RDI: 00000000fffffffe
RBP: 00000000fffffffe R08: 000000000000000e R09: 0000000000000000
R10: ffff888042014678 R11: ffffed10084028d3 R12: ffff8880464286a0
R13: dffffc0000000000 R14: ffff888046428668 R15: 0000000000000009
FS: 00007f5bd0f206c0(0000) GS:ffff88808ca55000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fab839e8000 CR3: 0000000033512000 CR4: 0000000000352ef0
Call Trace:
<TASK>
nilfs_bmap_mark+0xba/0x180 fs/nilfs2/bmap.c:402
nilfs_ioctl_mark_blocks_dirty fs/nilfs2/ioctl.c:764 [inline]
nilfs_ioctl_prepare_clean_segments+0x49a/0x800 fs/nilfs2/ioctl.c:799
nilfs_clean_segments+0x18c/0xa50 fs/nilfs2/segment.c:2525
nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:916 [inline]
nilfs_ioctl+0x261f/0x2780 fs/nilfs2/ioctl.c:1346
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5bcff9c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5bd0f20028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5bd0215fa0 RCX: 00007f5bcff9c799
RDX: 0000200000000640 RSI: 0000000040786e88 RDI: 0000000000000004
RBP: 00007f5bd0032c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5bd0216038 R14: 00007f5bd0215fa0 R15: 00007ffdf65e5358
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: [PATCH] nilfs2: fix missing continue after -ENOENT in nilfs_ioctl_mark_blocks_dirty()
Author: karti...@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master


nilfs_ioctl_mark_blocks_dirty() calls nilfs_bmap_lookup_at_level() to
get the current block number of each block descriptor. When the lookup
returns -ENOENT, meaning the block does not exist, it sets bd_blocknr
to 0 and continues processing.

However, if bd_oblocknr is also 0, the subsequent check:

if (bdescs[i].bd_blocknr != bdescs[i].bd_oblocknr)
continue;

will not skip the block, and nilfs_bmap_mark() will be called on a
non-existent block. This causes nilfs_btree_do_lookup() to return
-ENOENT, triggering the WARN_ON(ret == -ENOENT).

Fix this by adding a continue statement after setting bd_blocknr to 0
when the lookup returns -ENOENT, so that dead blocks are always skipped
regardless of the value of bd_oblocknr.

Fixes: 7942b919f732 ("nilfs2: ioctl operations")
Reported-by: syzbot+98a040...@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=98a040252119df0506f8
Signed-off-by: Deepanshu Kartikey <Karti...@gmail.com>
---
fs/nilfs2/ioctl.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index e17b8da66491..1615a314f557 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -745,6 +745,7 @@ static int nilfs_ioctl_mark_blocks_dirty(struct the_nilfs *nilfs,
if (ret != -ENOENT)
return ret;
bdescs[i].bd_blocknr = 0;
+ continue;
}
if (bdescs[i].bd_blocknr != bdescs[i].bd_oblocknr)
/* skip dead block */
--
2.43.0

[syzbot]

Hello,

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

failed to copy syz-executor to VM: failed to run ["scp" "-P" "3599" "-F" "/dev/null" "-o" "UserKnownHostsFile=/dev/null" "-o" "IdentitiesOnly=yes" "-o" "BatchMode=yes" "-o" "StrictHostKeyChecking=no" "-o" "ConnectTimeout=10" "/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/bin/linux_amd64/syz-executor" "root@localhost:/syz-executor"]: exit status 1



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-build2752091841=/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 c88105488a56
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: downloading golang.org/x/sys v0.41.0
go: downloading github.com/prometheus/common v0.67.5
go: downloading google.golang.org/protobuf v1.36.11
go: downloading github.com/prometheus/procfs v0.20.1
go list -f '{{.Stale}}' -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=c88105488a5620be13a34f467b1b811950c61bdd -X github.com/google/syzkaller/prog.gitRevisionDate=20260317-161255" ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=c88105488a5620be13a34f467b1b811950c61bdd -X github.com/google/syzkaller/prog.gitRevisionDate=20260317-161255" ./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=c88105488a5620be13a34f467b1b811950c61bdd -X github.com/google/syzkaller/prog.gitRevisionDate=20260317-161255" -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=\"c88105488a5620be13a34f467b1b811950c61bdd\"
go: downloading github.com/google/flatbuffers v25.12.19+incompatible
go: downloading golang.org/x/sync v0.19.0
go: downloading golang.org/x/exp v0.0.0-20260218203240-3dfff04db8fa
go: downloading google.golang.org/api v0.269.0
go: downloading cloud.google.com/go/spanner v1.88.0
go: downloading cloud.google.com/go/bigquery v1.74.0
go: downloading cloud.google.com/go/storage v1.60.0
go: downloading cloud.google.com/go/auth v0.18.2
go: downloading google.golang.org/grpc v1.79.1
go: downloading google.golang.org/genproto v0.0.0-20260226221140-a57be14db171
go: downloading go.opentelemetry.io/otel v1.40.0
go: downloading go.opentelemetry.io/otel/sdk/metric v1.40.0
go: downloading go.opentelemetry.io/otel/sdk v1.40.0
go: downloading github.com/googleapis/gax-go/v2 v2.17.0
go: downloading github.com/GoogleCloudPlatform/opentelemetry-operations-go/exporter/metric v0.55.0
go: downloading google.golang.org/genproto/googleapis/api v0.0.0-20260226221140-a57be14db171
go: downloading google.golang.org/genproto/googleapis/rpc v0.0.0-20260226221140-a57be14db171
go: downloading go.opentelemetry.io/otel/trace v1.40.0
go: downloading go.opentelemetry.io/contrib/detectors/gcp v1.40.0
go: downloading github.com/GoogleCloudPlatform/grpc-gcp-go/grpcgcp v1.6.0
go: downloading go.opentelemetry.io/otel/metric v1.40.0
go: downloading github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapping v0.55.0
go: downloading golang.org/x/oauth2 v0.35.0
go: downloading github.com/GoogleCloudPlatform/opentelemetry-operations-go/detectors/gcp v1.31.0
go: downloading github.com/klauspost/compress v1.18.4
go: downloading github.com/zeebo/xxh3 v1.1.0
go: downloading github.com/pierrec/lz4/v4 v4.1.25
go: downloading golang.org/x/net v0.51.0
go: downloading github.com/cncf/xds/go v0.0.0-20260202195803-dba9d589def2
go: downloading github.com/envoyproxy/go-control-plane/envoy v1.37.0
go: downloading cel.dev/expr v0.25.1
go: downloading github.com/envoyproxy/protoc-gen-validate v1.3.3
go: downloading golang.org/x/text v0.34.0
go: downloading github.com/googleapis/enterprise-certificate-proxy v0.3.12
go: downloading go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.65.0
go: downloading go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.65.0
go: downloading golang.org/x/crypto v0.48.0
/usr/bin/ld: /tmp/ccEER4Ht.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: 8a30aeb0 Merge tag 'nfsd-7.0-2' of git://git.kernel.or..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=d46eab0cfd31c214
dashboard link: https://syzkaller.appspot.com/bug?extid=98a040252119df0506f8
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=17e5a06a580000

[syzbot]

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
lost connection to test machine

Tested on:

commit: 8a30aeb0 Merge tag 'nfsd-7.0-2' of git://git.kernel.or..
git tree: upstream

console output: https://syzkaller.appspot.com/x/log.txt?x=10657352580000

kernel config: https://syzkaller.appspot.com/x/.config?x=d46eab0cfd31c214
dashboard link: https://syzkaller.appspot.com/bug?extid=98a040252119df0506f8
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=13d5a06a580000

[syzbot]

[syzbot]

Hello,

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

failed to copy syz-execprog to VM: failed to run ["scp" "-P" "28733" "-F" "/dev/null" "-o" "UserKnownHostsFile=/dev/null" "-o" "IdentitiesOnly=yes" "-o" "BatchMode=yes" "-o" "StrictHostKeyChecking=no" "-o" "ConnectTimeout=10" "/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/bin/linux_amd64/syz-execprog" "root@localhost:/syz-execprog"]: exit status 1

GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2210492039=/tmp/go-build -gno-record-gcc-switches'

go list -f '{{.Stale}}' -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=c88105488a5620be13a34f467b1b811950c61bdd -X github.com/google/syzkaller/prog.gitRevisionDate=20260317-161255" ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=c88105488a5620be13a34f467b1b811950c61bdd -X github.com/google/syzkaller/prog.gitRevisionDate=20260317-161255" ./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=c88105488a5620be13a34f467b1b811950c61bdd -X github.com/google/syzkaller/prog.gitRevisionDate=20260317-161255" -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=\"c88105488a5620be13a34f467b1b811950c61bdd\"

/usr/bin/ld: /tmp/ccvYSAc4.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: 8a30aeb0 Merge tag 'nfsd-7.0-2' of git://git.kernel.or..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=d46eab0cfd31c214
dashboard link: https://syzkaller.appspot.com/bug?extid=98a040252119df0506f8
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=153334ba580000