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Merge pull request #6814 from amjoseph-nixpkgs/pr/sandbox-error-messages

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local-derivation-goal.cc: improve error messages when sandboxing fails
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Théophane Hufschmitt 2022-07-22 13:27:52 +02:00 committed by GitHub
commit 2805439335
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2 changed files with 40 additions and 9 deletions
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39
src/libstore/build/local-derivation-goal.cc
View file

@ -845,18 +845,43 @@ void LocalDerivationGoal::startBuilder()
/* Some distros patch Linux to not allow unprivileged /* Some distros patch Linux to not allow unprivileged
* user namespaces. If we get EPERM or EINVAL, try * user namespaces. If we get EPERM or EINVAL, try
* without CLONE_NEWUSER and see if that works. * without CLONE_NEWUSER and see if that works.
* Details: https://salsa.debian.org/kernel-team/linux/-/commit/d98e00eda6bea437e39b9e80444eee84a32438a6
*/ */
usingUserNamespace = false; usingUserNamespace = false;
flags &= ~CLONE_NEWUSER; flags &= ~CLONE_NEWUSER;
child = clone(childEntry, stack + stackSize, flags, this); child = clone(childEntry, stack + stackSize, flags, this);
} }
/* Otherwise exit with EPERM so we can handle this in the if (child == -1) {
parent. This is only done when sandbox-fallback is set switch(errno) {
to true (the default). */ case EPERM:
if (child == -1 && (errno == EPERM || errno == EINVAL) && settings.sandboxFallback) case EINVAL: {
_exit(1); int errno_ = errno;
if (child == -1) throw SysError("cloning builder process"); if (!userNamespacesEnabled && errno==EPERM)
notice("user namespaces appear to be disabled; they are required for sandboxing; check /proc/sys/user/max_user_namespaces");
if (userNamespacesEnabled) {
Path procSysKernelUnprivilegedUsernsClone = "/proc/sys/kernel/unprivileged_userns_clone";
if (pathExists(procSysKernelUnprivilegedUsernsClone)
&& trim(readFile(procSysKernelUnprivilegedUsernsClone)) == "0") {
notice("user namespaces appear to be disabled; they are required for sandboxing; check /proc/sys/kernel/unprivileged_userns_clone");
}
}
Path procSelfNsUser = "/proc/self/ns/user";
if (!pathExists(procSelfNsUser))
notice("/proc/self/ns/user does not exist; your kernel was likely built without CONFIG_USER_NS=y, which is required for sandboxing");
/* Otherwise exit with EPERM so we can handle this in the
parent. This is only done when sandbox-fallback is set
to true (the default). */
if (settings.sandboxFallback)
_exit(1);
/* Mention sandbox-fallback in the error message so the user
knows that having it disabled contributed to the
unrecoverability of this failure */
throw SysError(errno_, "creating sandboxed builder process using clone(), without sandbox-fallback");
}
default:
throw SysError("creating sandboxed builder process using clone()");
}
}
writeFull(builderOut.writeSide.get(), writeFull(builderOut.writeSide.get(),
fmt("%d %d\n", usingUserNamespace, child)); fmt("%d %d\n", usingUserNamespace, child));
_exit(0); _exit(0);

10
src/libutil/error.hh
View file

@ -204,13 +204,19 @@ public:
int errNo; int errNo;
template<typename... Args> template<typename... Args>
SysError(const Args & ... args) SysError(int errNo_, const Args & ... args)
: Error("") : Error("")
{ {
errNo = errno; errNo = errNo_;
auto hf = hintfmt(args...); auto hf = hintfmt(args...);
err.msg = hintfmt("%1%: %2%", normaltxt(hf.str()), strerror(errNo)); err.msg = hintfmt("%1%: %2%", normaltxt(hf.str()), strerror(errNo));
} }
template<typename... Args>
SysError(const Args & ... args)
: SysError(errno, args ...)
{
}
}; };
} }