Re: [syzbot] [media?] KASAN: slab-use-after-free Read in dvb_frontend_release (3)

[syzbot <syzbot+ae466a728017ec940b41@syzkaller.appspotmail.com>]

Hello,

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

_SRC_OVR (bus 0 bus_irq 10 global_irq 10 high level)
[    0.324084][    T0] ACPI: INT_SRC_OVR (bus 0 bus_irq 11 global_irq 11 high level)
[    0.324103][    T0] ACPI: Using ACPI (MADT) for SMP configuration information
[    0.324118][    T0] CPU topo: Max. logical packages:   1
[    0.324122][    T0] CPU topo: Max. logical dies:       1
[    0.324126][    T0] CPU topo: Max. dies per package:   1
[    0.324137][    T0] CPU topo: Max. threads per core:   2
[    0.324142][    T0] CPU topo: Num. cores per package:     1
[    0.324146][    T0] CPU topo: Num. threads per package:   2
[    0.324150][    T0] CPU topo: Allowing 2 present CPUs plus 0 hotplug CPUs
[    0.324260][    T0] PM: hibernation: Registered nosave memory: [mem 0x00000000-0x00000fff]
[    0.324270][    T0] PM: hibernation: Registered nosave memory: [mem 0x0009f000-0x000fffff]
[    0.324278][    T0] PM: hibernation: Registered nosave memory: [mem 0xbfffd000-0xffffffff]
[    0.324303][    T0] [gap 0xc0000000-0xfffbbfff] available for PCI devices
[    0.324309][    T0] Booting paravirtualized kernel on KVM
[    0.324320][    T0] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.457957][    T0] Zone ranges:
[    0.457966][    T0]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
[    0.457977][    T0]   DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
[    0.457985][    T0]   Normal   [mem 0x0000000100000000-0x000000023fffffff]
[    0.457993][    T0]   Device   empty
[    0.457998][    T0] Movable zone start for each node
[    0.458001][    T0] Early memory node ranges
[    0.458005][    T0]   node   0: [mem 0x0000000000001000-0x000000000009efff]
[    0.458011][    T0]   node   0: [mem 0x0000000000100000-0x00000000bfffcfff]
[    0.458019][    T0]   node   0: [mem 0x0000000100000000-0x0000000140000fff]
[    0.458025][    T0]   node   1: [mem 0x0000000140001000-0x000000023fffffff]
[    0.458034][    T0] Initmem setup node 0 [mem 0x0000000000001000-0x0000000140000fff]
[    0.458049][    T0] Initmem setup node 1 [mem 0x0000000140001000-0x000000023fffffff]
[    0.458095][    T0] On node 0, zone DMA: 1 pages in unavailable ranges
[    0.458339][    T0] On node 0, zone DMA: 97 pages in unavailable ranges
[    0.520754][    T0] On node 0, zone Normal: 3 pages in unavailable ranges
[    0.583334][    T0] setup_percpu: NR_CPUS:8 nr_cpumask_bits:2 nr_cpu_ids:2 nr_node_ids:2
[    0.584030][    T0] percpu: Embedded 72 pages/cpu s254408 r8192 d32312 u1048576
[    0.584054][    T0] pcpu-alloc: s254408 r8192 d32312 u1048576 alloc=1*2097152
[    0.584066][    T0] pcpu-alloc: [0] 0 1 
[    0.584177][    T0] kvm-guest: PV spinlocks enabled
[    0.584186][    T0] PV qspinlock hash table entries: 256 (order: 0, 4096 bytes, linear)
[    0.584203][    T0] Kernel command line: earlyprintk=serial net.ifnames=0 sysctl.kernel.hung_task_all_cpu_backtrace=1 ima_policy=tcb nf-conntrack-ftp.ports=20000 nf-conntrack-tftp.ports=20000 nf-conntrack-sip.ports=20000 nf-conntrack-irc.ports=20000 nf-conntrack-sane.ports=20000 binder.debug_mask=0 rcupdate.rcu_expedited=1 rcupdate.rcu_cpu_stall_cputime=1 no_hash_pointers page_owner=on sysctl.vm.nr_hugepages=4 sysctl.vm.nr_overcommit_hugepages=4 secretmem.enable=1 sysctl.max_rcu_stall_to_panic=1 msr.allow_writes=off coredump_filter=0xffff root=/dev/sda console=ttyS0 vsyscall=native numa=fake=2 kvm-intel.nested=1 spec_store_bypass_disable=prctl nopcid vivid.n_devs=64 vivid.multiplanar=1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2 netrom.nr_ndevs=32 rose.rose_ndevs=32 smp.csd_lock_timeout=100000 watchdog_thresh=55 workqueue.watchdog_thresh=140 sysctl.net.core.netdev_unregister_timeout_secs=140 dummy_hcd.num=32 max_loop=32 nbds_max=32 \
[    0.584229][    T0] Kernel command line: comedi.comedi_num_legacy_minors=4 panic_on_warn=1 BOOT_IMAGE=/boot/bzImage root=/dev/sda1 console=ttyS0
[    0.588483][    T0] Unknown kernel command line parameters "nbds_max=32", will be passed to user space.
[    0.588544][    T0] random: crng init done
[    0.588547][    T0] printk: log buffer data + meta data: 262144 + 917504 = 1179648 bytes
[    0.588761][    T0] software IO TLB: area num 2.
[    0.616645][    T0] Fallback order for Node 0: 0 1 
[    0.616664][    T0] Fallback order for Node 1: 1 0 
[    0.616678][    T0] Built 2 zonelists, mobility grouping on.  Total pages: 2097051
[    0.616685][    T0] Policy zone: Normal
[    0.617377][    T0] mem auto-init: stack:all(zero), heap alloc:on, heap free:off
[    0.617385][    T0] stackdepot: allocating hash table via alloc_large_system_hash
[    0.617395][    T0] stackdepot hash table entries: 1048576 (order: 12, 16777216 bytes, linear)
[    0.622068][    T0] stackdepot: allocating space for 8192 stack pools via memblock
[    1.210344][    T0] **********************************************************
[    1.210354][    T0] **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
[    1.210358][    T0] **                                                      **
[    1.210362][    T0] ** This system shows unhashed kernel memory addresses   **
[    1.210365][    T0] ** via the console, logs, and other interfaces. This    **
[    1.210369][    T0] ** might reduce the security of your system.            **
[    1.210373][    T0] **                                                      **
[    1.210376][    T0] ** If you see this message and you are not debugging    **
[    1.210380][    T0] ** the kernel, report this immediately to your system   **
[    1.210384][    T0] ** administrator!                                       **
[    1.210387][    T0] **                                                      **
[    1.210391][    T0] ** Use hash_pointers=always to force this mode off      **
[    1.210395][    T0] **                                                      **
[    1.210398][    T0] **   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
[    1.210402][    T0] **********************************************************
[    1.213877][    T0] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=2
[    1.344641][    T0] allocated 167772160 bytes of page_ext
[    1.344682][    T0] Node 0, zone      DMA: page owner found early allocated 0 pages
[    1.358368][    T0] Node 0, zone    DMA32: page owner found early allocated 21120 pages
[    1.362689][    T0] Node 0, zone   Normal: page owner found early allocated 130 pages
[    1.373648][    T0] Node 1, zone   Normal: page ownserialport: Connected to syzkaller.us-central1-c.ci-upstream-kasan-gce-smack-root-test-job-parallel-0 port 1 (session ID: 27e7da33582c2a1f5960f3e4d1e08a357e0ae697147fe044510b0304e2ed012c, active connections: 1).
er found early allocated 19848 pages
[    1.374121][    T0] Kernel/User page tables isolation: enabled
[    1.376324][    T0] Dynamic Preempt: full
[    1.377426][    T0] ------------[ cut here ]------------
[    1.377431][    T0] overflows_flex_counter_type(typeof(*ctx), pwq_tbl, __count)
[    1.377435][    T0] WARNING: kernel/workqueue.c:5373 at apply_wqattrs_prepare+0xa5/0x1f0, CPU#0: swapper/0/0
[    1.377461][    T0] Modules linked in:
[    1.377470][    T0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
[    1.377481][    T0] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
[    1.377488][    T0] RIP: 0010:apply_wqattrs_prepare+0xa5/0x1f0
[    1.377507][    T0] Code: d8 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 2b 01 00 00 8b 1b bf 05 00 00 00 89 de e8 55 2b 35 00 83 fb 06 0f 83 ce 00 00 00 90 <0f> 0b 90 48 c7 c0 60 61 5e 8d 48 c1 e8 03 42 80 3c 38 00 74 0c 48
[    1.377516][    T0] RSP: 0000:ffffffff8d807bf8 EFLAGS: 00010097
[    1.377524][    T0] RAX: ffffffff818e73bb RBX: 0000000000000000 RCX: ffffffff8d902f00
[    1.377531][    T0] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
[    1.377537][    T0] RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
[    1.377543][    T0] R10: dffffc0000000000 R11: fffffbfff1e912b7 R12: ffff88813fe749c8
[    1.377550][    T0] R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
[    1.377562][    T0] FS:  0000000000000000(0000) GS:ffff888126592000(0000) knlGS:0000000000000000
[    1.377572][    T0] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.377579][    T0] CR2: ffff88823ffff000 CR3: 000000000d9ba000 CR4: 00000000000000b0
[    1.377588][    T0] Call Trace:
[    1.377593][    T0]  <TASK>
[    1.377599][    T0]  __alloc_workqueue+0xfbe/0x1e70
[    1.377617][    T0]  alloc_workqueue_noprof+0xe3/0x210
[    1.377629][    T0]  ? is_dynamic_key+0xd6/0x1c0
[    1.377644][    T0]  ? __pfx_alloc_workqueue_noprof+0x10/0x10
[    1.377657][    T0]  ? __kmalloc_cache_noprof+0x3a6/0x690
[    1.377670][    T0]  ? workqueue_init_early+0x89b/0xcf0
[    1.377687][    T0]  workqueue_init_early+0xaac/0xcf0
[    1.377700][    T0]  ? __cpuhp_setup_state+0x46/0x60
[    1.377717][    T0]  ? __pfx_workqueue_init_early+0x10/0x10
[    1.377733][    T0]  ? register_trace_event+0x3f7/0x4b0
[    1.377749][    T0]  start_kernel+0x189/0x3d0
[    1.377760][    T0]  x86_64_start_reservations+0x24/0x30
[    1.377773][    T0]  x86_64_start_kernel+0x143/0x1c0
[    1.377786][    T0]  common_startup_64+0x13e/0x147
[    1.377804][    T0]  </TASK>
[    1.377810][    T0] Kernel panic - not syncing: kernel: panic_on_warn set ...
[    1.377816][    T0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
[    1.377827][    T0] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
[    1.377833][    T0] Call Trace:
[    1.377837][    T0]  <TASK>
[    1.377840][    T0]  vpanic+0x56c/0xa60
[    1.377856][    T0]  ? __pfx__printk+0x10/0x10
[    1.377868][    T0]  ? __pfx_vpanic+0x10/0x10
[    1.377881][    T0]  ? is_bpf_text_address+0x292/0x2b0
[    1.377894][    T0]  ? is_bpf_text_address+0x26/0x2b0
[    1.377914][    T0]  panic+0xc5/0xd0
[    1.377928][    T0]  ? __pfx_panic+0x10/0x10
[    1.377947][    T0]  ? common_startup_64+0x13e/0x147
[    1.377959][    T0]  __warn+0x315/0x4f0
[    1.377973][    T0]  ? apply_wqattrs_prepare+0xa5/0x1f0
[    1.377987][    T0]  ? apply_wqattrs_prepare+0xa5/0x1f0
[    1.378000][    T0]  __report_bug+0x29a/0x540
[    1.378020][    T0]  ? apply_wqattrs_prepare+0xa5/0x1f0
[    1.378033][    T0]  ? __pfx___report_bug+0x10/0x10
[    1.378049][    T0]  ? do_raw_spin_unlock+0xf6/0x210
[    1.378064][    T0]  ? _raw_spin_unlock_irqrestore+0x4c/0x80
[    1.378074][    T0]  ? rt_mutex_slowunlock+0x1cb/0x300
[    1.378088][    T0]  ? __pfx_rt_mutex_slowunlock+0x10/0x10
[    1.378102][    T0]  ? apply_wqattrs_prepare+0xa5/0x1f0
[    1.378115][    T0]  report_bug+0x16a/0x220
[    1.378130][    T0]  ? apply_wqattrs_prepare+0xa5/0x1f0
[    1.378142][    T0]  ? apply_wqattrs_prepare+0xa7/0x1f0
[    1.378155][    T0]  handle_bug+0x98/0x200
[    1.378168][    T0]  exc_invalid_op+0x1a/0x50
[    1.378179][    T0]  asm_exc_invalid_op+0x1a/0x20
[    1.378190][    T0] RIP: 0010:apply_wqattrs_prepare+0xa5/0x1f0
[    1.378203][    T0] Code: d8 48 c1 e8 03 42 0f b6 04 38 84 c0 0f 85 2b 01 00 00 8b 1b bf 05 00 00 00 89 de e8 55 2b 35 00 83 fb 06 0f 83 ce 00 00 00 90 <0f> 0b 90 48 c7 c0 60 61 5e 8d 48 c1 e8 03 42 80 3c 38 00 74 0c 48
[    1.378211][    T0] RSP: 0000:ffffffff8d807bf8 EFLAGS: 00010097
[    1.378219][    T0] RAX: ffffffff818e73bb RBX: 0000000000000000 RCX: ffffffff8d902f00
[    1.378226][    T0] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
[    1.378231][    T0] RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
[    1.378237][    T0] R10: dffffc0000000000 R11: fffffbfff1e912b7 R12: ffff88813fe749c8
[    1.378244][    T0] R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
[    1.378254][    T0]  ? apply_wqattrs_prepare+0x9b/0x1f0
[    1.378270][    T0]  ? apply_wqattrs_prepare+0x9b/0x1f0
[    1.378284][    T0]  __alloc_workqueue+0xfbe/0x1e70
[    1.378300][    T0]  alloc_workqueue_noprof+0xe3/0x210
[    1.378312][    T0]  ? is_dynamic_key+0xd6/0x1c0
[    1.378326][    T0]  ? __pfx_alloc_workqueue_noprof+0x10/0x10
[    1.378339][    T0]  ? __kmalloc_cache_noprof+0x3a6/0x690
[    1.378351][    T0]  ? workqueue_init_early+0x89b/0xcf0
[    1.378367][    T0]  workqueue_init_early+0xaac/0xcf0
[    1.378380][    T0]  ? __cpuhp_setup_state+0x46/0x60
[    1.378396][    T0]  ? __pfx_workqueue_init_early+0x10/0x10
[    1.378412][    T0]  ? register_trace_event+0x3f7/0x4b0
[    1.378426][    T0]  start_kernel+0x189/0x3d0
[    1.378436][    T0]  x86_64_start_reservations+0x24/0x30
[    1.378449][    T0]  x86_64_start_kernel+0x143/0x1c0
[    1.378462][    T0]  common_startup_64+0x13e/0x147
[    1.378479][    T0]  </TASK>


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-build634184225=/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='go1.24.4'
GOWORK=''
PKG_CONFIG='pkg-config'

git status (err=<nil>)
HEAD detached at 1e62d19825
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=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336"  ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336"  ./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=1e62d1982527c3b4e18df04d61f2560fa1f434cc -X github.com/google/syzkaller/prog.gitRevisionDate=20260213-152336"  -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=\"1e62d1982527c3b4e18df04d61f2560fa1f434cc\"
/usr/bin/ld: /tmp/ccZjc2ZB.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=17938152580000


Tested on:

commit:         8934827d Merge tag 'kmalloc_obj-treewide-v7.0-rc1' of ..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=5ca447d428dc7079
dashboard link: https://syzkaller.appspot.com/bug?extid=ae466a728017ec940b41
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=114b7c02580000