runc run/exec: ignore SIGURG #3368
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Foreground runc exec and runc run forwards all the signals (that it can) to the process being run. Since Go 1.14, go runtime uses SIGURG for async preemptive scheduling. This means that runc regularly receives SIGURG and, in case of foreground runc run/exec, it gets forwarded to the container process. For example: [kir@kir-rhat runc]$ sudo ./runc --debug exec xx67 sleep 1m ... DEBU[0000] child process in init() DEBU[0000] setns_init: about to exec DEBU[0000]signals.go:102 main.(*signalHandler).forward() sending signal to process urgent I/O condition DEBU[0000]signals.go:102 main.(*signalHandler).forward() sending signal to process urgent I/O condition DEBU[0000]signals.go:102 main.(*signalHandler).forward() sending signal to process urgent I/O condition ... Or, with slightly better debug messages from commit 58c1ff3: DEBU[0000]signals.go:102 main.(*signalHandler).forward() forwarding SIGURG to 819784 DEBU[0000]signals.go:102 main.(*signalHandler).forward() forwarding SIGURG to 819784 Obviously, this signal is an internal implementation detail of Go runtime, and should not be forwarded to the container process. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
kzys
approved these changes
Feb 7, 2022
AkihiroSuda
approved these changes
Feb 8, 2022
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Foreground runc exec and runc run forwards all the signals (that it can)
to the process being run.
Since Go 1.14, go runtime uses SIGURG for async preemptive scheduling.
This means that runc regularly receives SIGURG and, in case of
foreground runc run/exec, it gets forwarded to the container process.
For example:
[kir@kir-rhat runc]$ sudo ./runc --debug exec xx67 sleep 1m
...
DEBU[0000] child process in init()
DEBU[0000] setns_init: about to exec
DEBU[0000]signals.go:102 main.(*signalHandler).forward() sending signal to process urgent I/O condition
DEBU[0000]signals.go:102 main.(*signalHandler).forward() sending signal to process urgent I/O condition
DEBU[0000]signals.go:102 main.(*signalHandler).forward() sending signal to process urgent I/O condition
...
Or, with slightly better debug messages from commit 58c1ff3:
DEBU[0000]signals.go:102 main.(*signalHandler).forward() forwarding SIGURG to 819784
DEBU[0000]signals.go:102 main.(*signalHandler).forward() forwarding SIGURG to 819784
Obviously, this signal is an internal implementation detail of Go
runtime, and should not be forwarded to the container process.
Fixes: #3364