On Tue, Apr 30, 2019 at 11:47:51AM +0200, Michal Privoznik wrote:
If an FD is passed into a child using:
virCommandPassFD(cmd, fd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
then the parent should refrain from touching @fd thereafter. This
is even documented in virCommandPassFD() comment. The reason is
that either at virCommandRun()/virCommandRunAsync() or
virCommandFree() time the @fd will be closed. Closing it earlier,
e.g. right after virCommandPassFD() call might result in
undesired results. Another thread might open a file and receive
the same FD which is then unexpectedly closed by virCommandFree()
or virCommandRun().
Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
src/qemu/qemu_command.c | 10 ++++++----
src/util/virpolkit.c | 1 +
tests/commandtest.c | 2 +-
3 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index bf1fb539b1..92bd1524db 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -8978,17 +8978,19 @@ qemuBuildInterfaceCommandLine(virQEMUDriverPtr driver,
if (qemuSecuritySetTapFDLabel(driver->securityManager,
def, tapfd[i]) < 0)
goto cleanup;
- virCommandPassFD(cmd, tapfd[i],
- VIR_COMMAND_PASS_FD_CLOSE_PARENT);
if (virAsprintf(&tapfdName[i], "%d", tapfd[i]) < 0)
goto cleanup;
+ virCommandPassFD(cmd, tapfd[i],
+ VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+ tapfd[i] = -1;
}
for (i = 0; i < vhostfdSize; i++) {
- virCommandPassFD(cmd, vhostfd[i],
- VIR_COMMAND_PASS_FD_CLOSE_PARENT);
if (virAsprintf(&vhostfdName[i], "%d", vhostfd[i]) < 0)
goto cleanup;
+ virCommandPassFD(cmd, vhostfd[i],
+ VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+ vhostfd[i] = -1;
This won't play nicely with the cleanup section, where we stop the
cleanup on the first -1 encountered:
for (i = 0; vhostfd && i < vhostfdSize && vhostfd[i] >= 0; i++) {
for (i = 0; tapfd && i < tapfdSize && tapfd[i] >= 0; i++) {
But it seems it's just a micro-optimization.
With the >= 0 conditions removed:
Reviewed-by: Ján Tomko <jtomko@xxxxxxxxxx>
Jano
}
if (chardev)
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