Re: [syzbot] [fs?] KASAN: slab-use-after-free Read in lookup_noperm_common

[syzbot <syzbot+23ad911c819b923238b7@syzkaller.appspotmail.com>]

Hello,

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

[    5.732350][    T1] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
[    5.732431][    T1] software IO TLB: mapped [mem 0x00000000b4600000-0x00000000b8600000] (64MB)
[    5.752193][    T1] ACPI: bus type thunderbolt registered
[    5.772890][    T1] RAPL PMU: API unit is 2^-32 Joules, 0 fixed counters, 10737418240 ms ovfl timer
[    5.790038][   T69] kworker/u8:4 (69) used greatest stack depth: 28424 bytes left
[    5.791790][   T70] kworker/u8:4 (70) used greatest stack depth: 26568 bytes left
[    5.839556][    T1] kvm_amd: CPU 1 isn't AMD or Hygon
[    5.839594][    T1] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x1fb63109b96, max_idle_ns: 440795265316 ns
[    5.840420][    T1] clocksource: Switched to clocksource tsc
[    5.951079][    T1] Initialise system trusted keyrings
[    5.957064][    T1] workingset: timestamp_bits=40 (anon: 35) max_order=21 bucket_order=0 (anon: 0)
[    5.982234][    T1] DLM installed
[    5.994295][    T1] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[    6.015885][    T1] NFS: Registering the id_resolver key type
[    6.016165][    T1] Key type id_resolver registered
[    6.016181][    T1] Key type id_legacy registered
[    6.016602][    T1] nfs4filelayout_init: NFSv4 File Layout Driver Registering...
[    6.016835][    T1] nfs4flexfilelayout_init: NFSv4 Flexfile Layout Driver Registering...
[    6.022936][    T1] smbdirect: subsystem loading...
[    6.074501][    T1] smbdirect: subsystem loaded
[    6.115421][    T1] Key type cifs.spnego registered
[    6.115810][    T1] Key type cifs.idmap registered
[    6.122543][    T1] ntfs3: Enabled Linux POSIX ACLs support
[    6.122558][    T1] ntfs3: Read-only LZX/Xpress compression included
[    6.123157][    T1] jffs2: version 2.2. (NAND) (SUMMARY)  © 2001-2006 Red Hat, Inc.
[    6.133153][    T1] romfs: ROMFS MTD (C) 2007 Red Hat, Inc.
[    6.135119][    T1] QNX4 filesystem 0.2.3 registered.
[    6.137491][    T1] qnx6: QNX6 filesystem 1.0.0 registered.
[    6.145880][    T1] fuse: init (API version 7.45)
[    6.171786][    T1] orangefs_debugfs_init: called with debug mask: :none: :0:
[    6.178859][    T1] orangefs_init: module version upstream loaded
[    6.183145][    T1] JFS: nTxBlock = 8192, nTxLock = 65536
[    6.222021][    T1] SGI XFS with ACLs, security attributes, realtime, scrub, repair, quota, no debug enabled
[    6.240797][    T1] 9p: Installing v9fs 9p2000 file system support
[    6.241949][    T1] NILFS version 2 loaded
[    6.241962][    T1] befs: version: 0.9.3
[    6.243535][    T1] ocfs2: Registered cluster interface o2cb
[    6.248029][    T1] ocfs2: Registered cluster interface user
[    6.257098][    T1] OCFS2 User DLM kernel interface loaded
[    6.315750][    T1] gfs2: GFS2 installed
[    6.341989][    T1] ceph: loaded (mds proto 32)
[    6.361174][    T1] NET: Registered PF_ALG protocol family
[    6.361720][    T1] async_tx: api initialized (async)
[    6.361785][    T1] Key type asymmetric registered
[    6.361874][    T1] Asymmetric key parser 'x509' registered
[    6.361891][    T1] Asymmetric key parser 'pkcs8' registered
[    6.361907][    T1] Key type pkcs7_test registered
[    6.363323][    T1] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 239)
[    6.382957][    T1] io scheduler mq-deadline registered
[    6.383009][    T1] io scheduler kyber registered
[    6.384939][    T1] io scheduler bfq registered
[    6.390095][    T1] raid6: skipped pq benchmark and selected avx2x4
[    6.436166][  T142] kworker/u8:2 (142) used greatest stack depth: 26432 bytes left
[    6.482050][    T1] input: Power Button as /devices/platform/LNXPWRBN:00/input/input0
[    6.494178][    T1] ACPI: button: Power Button [PWRF]
[    6.508253][    T1] input: Sleep Button as /devices/platform/LNXSLPBN:00/input/input1
[    6.512601][    T1] ACPI: button: Sleep Button [SLPF]
[    6.564085][    T1] ioatdma: Intel(R) QuickData Technology Driver 5.00
[    6.620644][   T10] ACPI: \_SB_.LNKC: Enabled at IRQ 11
[    6.621000][   T10] virtio-pci 0000:00:03.0: virtio_pci: leaving for legacy driver
[    6.683103][   T10] ACPI: \_SB_.LNKD: Enabled at IRQ 10
[    6.683331][   T10] virtio-pci 0000:00:04.0: virtio_pci: leaving for legacy driver
[    6.748091][   T10] ACPI: \_SB_.LNKB: Enabled at IRQ 10
[    6.748252][   T10] virtio-pci 0000:00:06.0: virtio_pci: leaving for legacy driver
[    6.795198][   T10] virtio-pci 0000:00:07.0: virtio_pci: leaving for legacy driver
[    8.005073][    T1] N_HDLC line discipline registered with maxframe=4096
[    8.008071][    T1] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[    8.038848][    T1] 00:02: ttyS0 I/O:0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    8.078361][    T1] 00:03: ttyS1 I/O:0x2f8 (irq = 3, base_baud = 115200) is a 16550A
[    8.112459][    T1] 00:04: ttyS2 I/O:0x3e8 (irq = 6, base_baud = 115200) is a 16550A
[    8.147922][    T1] 00:05: ttyS3 I/O:0x2e8 (irq = 7, base_baud = 115200) is a 16550A
[    8.215592][    T1] Non-volatile memory driver v1.3
[    8.265200][    T1] usbcore: registered new interface driver xillyusb
[    8.279638][    T1] ACPI: bus type drm_connector registered
[    8.301506][    T1] [drm] Initialized vgem 1.0.0 for vgem on minor 0
[    8.318886][    T1] ------------[ cut here ]------------
[    8.318903][    T1] [PLANE:35:plane-0] pixel format with alpha exposed but blend mode not setup
[    8.318927][    T1] WARNING: drivers/gpu/drm/drm_mode_config.c:873 at drm_mode_config_validate+0x1c6d/0x1e60, CPU#1: swapper/0/1
[    8.319003][    T1] Modules linked in:
[    8.319061][    T1] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
[    8.319088][    T1] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
[    8.319112][    T1] RIP: 0010:drm_mode_config_validate+0x1cae/0x1e60
[    8.319151][    T1] Code: 0f 85 ae 00 00 00 4d 8d 77 10 8b 6d 00 4c 89 f0 48 c1 e8 03 80 3c 18 00 74 08 4c 89 f7 e8 7a d4 ac fc 49 8b 16 4c 89 ef 89 ee <67> 48 0f b9 3a eb 05 e8 86 05 40 fc 49 bd 00 00 00 00 00 fc ff df
[    8.319177][    T1] RSP: 0000:ffffc90000067810 EFLAGS: 00010246
[    8.319197][    T1] RAX: 1ffff11004cf3e08 RBX: dffffc0000000000 RCX: ffff88801c6f5dc0
[    8.319215][    T1] RDX: ffff8880262defc0 RSI: 0000000000000023 RDI: ffffffff8fdc85b0
[    8.319233][    T1] RBP: 0000000000000023 R08: 0000000000000000 R09: 0000000000000000
[    8.319246][    T1] R10: dffffc0000000000 R11: fffffbfff1fa2790 R12: dffffc0000000000
[    8.319263][    T1] R13: ffffffff8fdc85b0 R14: ffff88802679f040 R15: ffff88802679f030
[    8.319283][    T1] FS:  0000000000000000(0000) GS:ffff888125ada000(0000) knlGS:0000000000000000
[    8.319303][    T1] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    8.319319][    T1] CR2: 0000000000000000 CR3: 000000000e1b0000 CR4: 00000000003526f0
[    8.319344][    T1] Call Trace:
[    8.319353][    T1]  <TASK>
[    8.319379][    T1]  ? debugfs_create_file_full+0x3f/0x60
[    8.319413][    T1]  drm_dev_register+0x7f/0xd80
[    8.319449][    T1]  vkms_create+0x40d/0x4f0
[    8.319473][    T1]  ? __pfx_vkms_init+0x10/0x10
[    8.319508][    T1]  vkms_init+0x57/0x80
[    8.319537][    T1]  do_one_initcall+0x250/0x870
[    8.319596][    T1]  ? __pfx_vkms_init+0x10/0x10
[    8.319626][    T1]  ? __pfx_do_one_initcall+0x10/0x10
[    8.319660][    T1]  ? lapic_next_event+0x11/0x20
[    8.319701][    T1]  ? __pfx_clockevents_program_event+0x10/0x10
[    8.319735][    T1]  ? __pfx___schedule+0x10/0x10
[    8.319795][    T1]  ? irqentry_exit+0x218/0x8f0
[    8.319827][    T1]  ? lockdep_hardirqs_on+0x7a/0x110
[    8.319858][    T1]  ? irqentry_exit+0x218/0x8f0
[    8.319886][    T1]  ? trace_irq_disable+0x3b/0x140
[    8.319930][    T1]  ? next_arg+0x4a0/0x5e0
[    8.319965][    T1]  ? parameq+0x14d/0x170
[    8.320005][    T1]  ? parse_args+0x9c3/0xad0
[    8.320059][    T1]  ? trace_kmalloc+0x2a/0xf0
[    8.320083][    T1]  ? rcu_is_watching+0x15/0xb0
[    8.320117][    T1]  do_initcall_level+0x10a/0x1a0
[    8.320154][    T1]  ? kernel_init+0x22/0x1d0
[    8.320191][    T1]  do_initcalls+0x59/0xa0
[    8.320227][    T1]  kernel_init_freeable+0x29d/0x3e0
[    8.320263][    T1]  ? __pfx_kernel_init+0x10/0x10
[    8.320302][    T1]  kernel_init+0x22/0x1d0
[    8.320344][    T1]  ? __pfx_kernel_init+0x10/0x10
[    8.320380][    T1]  ret_from_fork+0x514/0xb70
[    8.320418][    T1]  ? __pfx_ret_from_fork+0x10/0x10
[    8.320452][    T1]  ? __switch_to+0xc89/0x1420
[    8.320485][    T1]  ? __pfx_kernel_init+0x10/0x10
[    8.320525][    T1]  ret_from_fork_asm+0x1a/0x30
[    8.320577][    T1]  </TASK>
[    8.320595][    T1] Kernel panic - not syncing: kernel: panic_on_warn set ...
[    8.320612][    T1] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
[    8.320637][    T1] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
[    8.320651][    T1] Call Trace:
[    8.320660][    T1]  <TASK>
[    8.320669][    T1]  vpanic+0x56c/0xa60
[    8.320694][    T1]  ? __pfx__printk+0x10/0x10
[    8.320724][    T1]  ? __pfx_vpanic+0x10/0x10
[    8.320746][    T1]  ? is_bpf_text_address+0x292/0x2b0
[    8.320775][    T1]  ? is_bpf_text_address+0x26/0x2b0
[    8.320813][    T1]  panic+0xc5/0xd0
[    8.320837][    T1]  ? __pfx_panic+0x10/0x10
[    8.320872][    T1]  ? ret_from_fork_asm+0x1a/0x30
[    8.320911][    T1]  __warn+0x315/0x4c0
[    8.320934][    T1]  ? drm_mode_config_validate+0x1c6d/0x1e60
[    8.320970][    T1]  ? drm_mode_config_validate+0x1c6d/0x1e60
[    8.321002][    T1]  __report_bug+0x276/0x570
[    8.321038][    T1]  ? drm_mode_config_validate+0x1c6d/0x1e60
[    8.321073][    T1]  ? __pfx___report_bug+0x10/0x10
[    8.321112][    T1]  ? _raw_spin_unlock_irqrestore+0x30/0x80
[    8.321144][    T1]  ? lockdep_hardirqs_on+0x7a/0x110
[    8.321177][    T1]  ? rt_mutex_slowunlock+0x4ee/0xa20
[    8.321205][    T1]  report_bug_entry+0x19a/0x290
[    8.321246][    T1]  ? drm_mode_config_validate+0x1cae/0x1e60
[    8.321277][    T1]  ? drm_mode_config_validate+0x1cb3/0x1e60
[    8.321313][    T1]  handle_bug+0xce/0x200
[    8.321505][    T1]  exc_invalid_op+0x1a/0x50
[    8.321542][    T1]  asm_exc_invalid_op+0x1a/0x20
[    8.321565][    T1] RIP: 0010:drm_mode_config_validate+0x1cae/0x1e60
[    8.321598][    T1] Code: 0f 85 ae 00 00 00 4d 8d 77 10 8b 6d 00 4c 89 f0 48 c1 e8 03 80 3c 18 00 74 08 4c 89 f7 e8 7a d4 ac fc 49 8b 16 4c 89 ef 89 ee <67> 48 0f b9 3a eb 05 e8 86 05 40 fc 49 bd 00 00 00 00 00 fc ff df
[    8.321616][    T1] RSP: 0000:ffffc90000067810 EFLAGS: 00010246
[    8.321634][    T1] RAX: 1ffff11004cf3e08 RBX: dffffc0000000000 RCX: ffff88801c6f5dc0
[    8.321652][    T1] RDX: ffff8880262defc0 RSI: 0000000000000023 RDI: ffffffff8fdc85b0
[    8.321667][    T1] RBP: 0000000000000023 R08: 0000000000000000 R09: 0000000000000000
[    8.321680][    T1] R10: dffffc0000000000 R11: fffffbfff1fa2790 R12: dffffc0000000000
[    8.321696][    T1] R13: ffffffff8fdc85b0 R14: ffff88802679f040 R15: ffff88802679f030
[    8.321739][    T1]  ? debugfs_create_file_full+0x3f/0x60
[    8.321769][    T1]  drm_dev_register+0x7f/0xd80
[    8.321803][    T1]  vkms_create+0x40d/0x4f0
[    8.321826][    T1]  ? __pfx_vkms_init+0x10/0x10
[    8.321853][    T1]  vkms_init+0x57/0x80
[    8.321880][    T1]  do_one_initcall+0x250/0x870
[    8.321912][    T1]  ? __pfx_vkms_init+0x10/0x10
[    8.322067][    T1]  ? __pfx_do_one_initcall+0x10/0x10
[    8.322100][    T1]  ? lapic_next_event+0x11/0x20
[    8.322140][    T1]  ? __pfx_clockevents_program_event+0x10/0x10
[    8.322179][    T1]  ? __pfx___schedule+0x10/0x10
[    8.322219][    T1]  ? irqentry_exit+0x218/0x8f0
[    8.322248][    T1]  ? lockdep_hardirqs_on+0x7a/0x110
[    8.322278][    T1]  ? irqentry_exit+0x218/0x8f0
[    8.322306][    T1]  ? trace_irq_disable+0x3b/0x140
[    8.322379][    T1]  ? next_arg+0x4a0/0x5e0
[    8.322415][    T1]  ? parameq+0x14d/0x170
[    8.322452][    T1]  ? parse_args+0x9c3/0xad0
[    8.322503][    T1]  ? trace_kmalloc+0x2a/0xf0
[    8.322526][    T1]  ? rcu_is_watching+0x15/0xb0
[    8.322558][    T1]  do_initcall_level+0x10a/0x1a0
[    8.322594][    T1]  ? kernel_init+0x22/0x1d0
[    8.322629][    T1]  do_initcalls+0x59/0xa0
[    8.322664][    T1]  kernel_init_freeable+0x29d/0x3e0
[    8.322697][    T1]  ? __pfx_kernel_init+0x10/0x10
[    8.322736][    T1]  kernel_init+0x22/0x1d0
[    8.322776][    T1]  ? __pfx_kernel_init+0x10/0x10
[    8.322815][    T1]  ret_from_fork+0x514/0xb70
[    8.322850][    T1]  ? __pfx_ret_from_fork+0x10/0x10
[    8.322880][    T1]  ? __switch_to+0xc89/0x1420
[    8.322912][    T1]  ? __pfx_kernel_init+0x10/0x10
[    8.322957][    T1]  ret_from_fork_asm+0x1a/0x30
[    8.323005][    T1]  </TASK>
[    8.323640][    T1] Kernel Offset: disabled


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-build712057134=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/syzkaller/jobs-2/linux/gopath/src/github.com/google/syzkaller/go.mod'
GOMODCACHE='/syzkaller/jobs-2/linux/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/syzkaller/jobs-2/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 cb1587ea08
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=cb1587ea08e5a1a12acb4372efe923e2308effdb -X github.com/google/syzkaller/prog.gitRevisionDate=20260729-121857"  ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=cb1587ea08e5a1a12acb4372efe923e2308effdb -X github.com/google/syzkaller/prog.gitRevisionDate=20260729-121857"  ./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=cb1587ea08e5a1a12acb4372efe923e2308effdb -X github.com/google/syzkaller/prog.gitRevisionDate=20260729-121857"  -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=\"cb1587ea08e5a1a12acb4372efe923e2308effdb\"
/usr/bin/ld: /tmp/ccASjCJk.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


Error text is too large and was truncated, full error text is at:
https://syzkaller.appspot.com/x/error.txt?x=1389b8c6580000


Tested on:

commit:         78bc8af4 Add linux-next specific files for 20260729
git tree:       linux-next
kernel config:  https://syzkaller.appspot.com/x/.config?x=9e610c4fe458e456
dashboard link: https://syzkaller.appspot.com/bug?extid=23ad911c819b923238b7
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=121025b9580000