Re: [syzbot] [fuse?] INFO: task hung in fuse_chan_send

[syzbot <syzbot+a531d1b1fb0fa2a75a73@syzkaller.appspotmail.com>]

Hello,

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

lost connection to test machine



syzkaller login: qemu-system-x86_64: ahci: PRDT length for NCQ command (0x0) is smaller than the requested size (0xba000)
[  110.222965][ T1028] ata1.00: Read log 0x10 page 0x00 failed, Emask 0x1
[  110.225835][ T1028] ata1: failed to read log page 10h (errno=-5)
[  110.228573][ T1028] ata1.00: exception Emask 0x1 SAct 0xc000 SErr 0x0 action 0x0
[  110.243158][ T1028] ata1.00: irq_stat 0x40000000
[  110.247818][ T1028] ata1.00: failed command: WRITE FPDMA QUEUED
[  110.255077][ T1028] ata1.00: cmd 61/d0:70:36:41:04/05:00:00:00:00/40 tag 14 ncq dma 761856 out
[  110.255077][ T1028]          res 50/00:00:00:00:00/00:00:00:00:00/00 Emask 0x1 (device error)
[  110.273090][ T1028] ata1.00: status: { DRDY }
[  110.280653][ T1028] ata1.00: failed command: WRITE FPDMA QUEUED
[  110.291935][ T1028] ata1.00: cmd 61/e8:78:06:47:04/02:00:00:00:00/40 tag 15 ncq dma 380928 out
[  110.291935][ T1028]          res 50/00:00:00:00:00/00:00:00:00:00/00 Emask 0x1 (device error)
[  110.317045][ T1028] ata1.00: status: { DRDY }
[  110.325648][ T1028] ata1.00: configured for UDMA/100
[  110.332172][ T1028] ata1: EH complete
qemu-system-x86_64: ahci: PRDT length for NCQ command (0x0) is smaller than the requested size (0x400000)
qemu-system-x86_64: ahci: PRDT length for NCQ command (0x0) is smaller than the requested size (0x400000)
Warning: Permanently added '[localhost]:55333' (ED25519) to the list of known hosts.
2026/07/24 10:48:22 parsed 1 programs
2026/07/24 10:48:22 serving rpc on tcp://33671
[  120.451810][ T5301] cgroup: Unknown subsys name 'net'
[  120.509463][ T5301] cgroup: Unknown subsys name 'cpuset'
[  120.516681][ T5301] cgroup: Unknown subsys name 'rlimit'
[  137.844799][ T1332] ieee802154 phy0 wpan0: encryption failed: -22
[  137.847636][ T1332] ieee802154 phy1 wpan1: encryption failed: -22
[  178.182256][ T1028] ata1.00: NCQ disabled due to excessive errors
[  178.184972][ T1028] ata1.00: exception Emask 0x0 SAct 0x120 SErr 0x0 action 0x6 frozen
[  178.188645][ T1028] ata1.00: failed command: WRITE FPDMA QUEUED
[  178.191451][ T1028] ata1.00: cmd 61/00:28:36:01:05/20:00:00:00:00/40 tag 5 ncq dma 4194304 ou
[  178.191451][ T1028]          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[  178.199514][ T1028] ata1.00: status: { DRDY }
[  178.202584][ T1028] ata1.00: failed command: WRITE FPDMA QUEUED
[  178.205241][ T1028] ata1.00: cmd 61/00:40:36:61:05/20:00:00:00:00/40 tag 8 ncq dma 4194304 ou
[  178.205241][ T1028]          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[  178.213219][ T1028] ata1.00: status: { DRDY }
[  178.215375][ T1028] ata1: hard resetting link
[  178.533841][ T1028] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[  178.537972][ T1028] ata1.00: configured for UDMA/100
[  178.540726][ T1028] ata1: EH complete
qemu-system-x86_64: hw/ide/core.c:934: ide_dma_cb: Assertion `prep_size >= 0 && prep_size <= n * 512' failed.
Connection to localhost closed by remote host.


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-build793079094=/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 fb92f11c47
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=fb92f11c4789d9647a75c09c983dbee5c8488ccf -X github.com/google/syzkaller/prog.gitRevisionDate=20260626-134956"  ./sys/syz-sysgen | grep -q false || go install -ldflags="-s -w -X github.com/google/syzkaller/prog.GitRevision=fb92f11c4789d9647a75c09c983dbee5c8488ccf -X github.com/google/syzkaller/prog.gitRevisionDate=20260626-134956"  ./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=fb92f11c4789d9647a75c09c983dbee5c8488ccf -X github.com/google/syzkaller/prog.gitRevisionDate=20260626-134956"  -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=\"fb92f11c4789d9647a75c09c983dbee5c8488ccf\"
/usr/bin/ld: /tmp/ccLzPndg.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:         48a5a7ab Merge tag 'v7.2-rc4-smb3-client-fixes' of git..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=3c3d59be33cf7e9a
dashboard link: https://syzkaller.appspot.com/bug?extid=a531d1b1fb0fa2a75a73
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=137f59c1580000