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Add a test case for a deadlock.

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The CGO_ENABLED=0 failure mode is discussed in:

  https://github.com/golang/go/issues/50113

At the present time, this only passes when the psx package is compiled
CGO_ENABLED=1. The problem being that a blocking read cannot be
interrupted by the CGO_ENABLED=0 build of package "psx". It does not
deadlock when compiled CGO_ENABLED=1 because the psx signal wakes the
reading thread up back into user space.

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
This commit is contained in:
Andrew G. Morgan 2022-01-23 16:35:23 -08:00
parent f25a1b7e69
commit bbabfb4cf4
3 changed files with 44 additions and 3 deletions
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2
go/.gitignore vendored
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@ -2,6 +2,8 @@ good-names.go
compare-cap
try-launching
try-launching-cgo
psx-fd
psx-fd-cgo
psx-signals
psx-signals-cgo
b210613

20
go/Makefile
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@ -83,6 +83,18 @@ ifeq ($(CGO_REQUIRED),0)
CC="$(CC)" CGO_ENABLED="1" $(CGO_LDFLAGS_ALLOW) $(GO) build $(GO_BUILD_FLAGS) -mod=vendor -o $@-cgo $<
endif
# This is a test case developed from the deadlock investigation,
# https://github.com/golang/go/issues/50113 . Note the psx-fd.go code
# works when compiled CGO_ENABLED=1, but deadlocks when compiled
# CGO_ENABLED=0. At the time of writing, this is true for go1.16+.
psx-fd: psx-fd.go PSXGOPACKAGE
CC="$(CC)" CGO_ENABLED="$(CGO_REQUIRED)" $(CGO_LDFLAGS_ALLOW) $(GO) build $(GO_BUILD_FLAGS) -mod=vendor -o $@ $<
ifeq ($(CGO_REQUIRED),0)
psx-fd-cgo: psx-fd.go PSXGOPACKAGE
CC="$(CC)" CGO_ENABLED="1" $(CGO_LDFLAGS_ALLOW) $(GO) build $(GO_BUILD_FLAGS) -mod=vendor -o $@ $<
endif
psx-signals: psx-signals.go PSXGOPACKAGE
CC="$(CC)" CGO_ENABLED="$(CGO_REQUIRED)" $(CGO_LDFLAGS_ALLOW) CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) build $(GO_BUILD_FLAGS) -mod=vendor $<
@ -110,16 +122,18 @@ mismatch-cgo: mismatch.go CAPGOPACKAGE
CC="$(CC)" CGO_ENABLED="1" $(CGO_LDFLAGS_ALLOW) CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) build $(GO_BUILD_FLAGS) -mod=vendor -o $@ $<
endif
test: setid gowns captree $(TESTS)
test: setid gowns captree psx-fd $(TESTS)
CC="$(CC)" CGO_ENABLED="$(CGO_REQUIRED)" $(CGO_LDFLAGS_ALLOW) $(GO) test -mod=vendor $(IMPORTDIR)/psx
CC="$(CC)" CGO_ENABLED="$(CGO_REQUIRED)" $(CGO_LDFLAGS_ALLOW) $(GO) test -mod=vendor $(IMPORTDIR)/cap
LD_LIBRARY_PATH=../libcap ./compare-cap
./psx-signals
./mismatch || exit 0 ; exit 1
timeout 5 ./psx-fd || echo "this is a known Go bug"
ifeq ($(CGO_REQUIRED),0)
$(MAKE) psx-signals-cgo mismatch-cgo
$(MAKE) psx-signals-cgo mismatch-cgo psx-fd-cgo
./psx-signals-cgo
./mismatch-cgo || exit 0 ; exit 1
./psx-fd-cgo
endif
./setid --caps=false
./gowns -- -c "echo gowns runs"
@ -167,5 +181,5 @@ clean:
rm -f compare-cap try-launching try-launching-cgo
rm -f $(topdir)/cap/*~ $(topdir)/psx/*~
rm -f b210613 b215283 b215283-cgo psx-signals psx-signals-cgo
rm -f mismatch mismatch-cgo
rm -f mismatch mismatch-cgo psx-fd psx-fd-cgo
rm -fr vendor CAPGOPACKAGE PSXGOPACKAGE go.sum

25
go/psx-fd.go Normal file
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@ -0,0 +1,25 @@
package main
import (
"log"
"os"
"syscall"
"time"
"kernel.org/pub/linux/libs/security/libcap/psx"
)
const prSetKeepCaps = 8
func main() {
r, w, err := os.Pipe()
if err != nil {
log.Fatalf("failed to obtain pipe: %v", err)
}
data := make([]byte, 2+r.Fd())
go r.Read(data)
time.Sleep(500 * time.Millisecond)
psx.Syscall3(syscall.SYS_PRCTL, prSetKeepCaps, 1, 0)
w.Close()
r.Close()
}