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Kernel: Fix bug where we half apply pledges in sys$pledge(..)

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This bug manifests it self when the caller to sys$pledge() passes valid
promises, but invalid execpromises. The code would apply the promises
and then return an error for the execpromises. This leaves the user in
a confusing state, as the promises were silently applied, but we return
an error suggesting the operation has failed.

Avoid this situation by tweaking the implementation to only apply the
promises / execpromises after all validation has occurred.
This commit is contained in:
Brian Gianforcaro 2021-07-23 09:21:43 -07:00 • committed by Andreas Kling
parent 36ff717c54
commit e4b86aa5d8
1 changed files with 17 additions and 6 deletions
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23
Kernel/Syscalls/pledge.cpp
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@ -52,22 +52,33 @@ KResultOr<FlatPtr> Process::sys$pledge(Userspace<const Syscall::SC_pledge_params
ProtectedDataMutationScope scope { *this };
u32 new_promises = 0;
if (promises) {
u32 new_promises = 0;
if (!parse_pledge(promises->view(), new_promises))
return EINVAL;
if (m_has_promises && (new_promises & ~m_promises))
return EPERM;
}
u32 new_execpromises = 0;
if (execpromises) {
if (!parse_pledge(execpromises->view(), new_execpromises))
return EINVAL;
if (m_has_execpromises && (new_execpromises & ~m_execpromises))
return EPERM;
}
// Only apply promises after all validation has occurred, this ensures
// we don't introduce logic bugs like applying the promises, and then
// erroring out when parsing the exec promises later. Such bugs silently
// leave the caller in an unexpected state.
if (promises) {
m_has_promises = true;
m_promises = new_promises;
}
if (execpromises) {
u32 new_execpromises = 0;
if (!parse_pledge(execpromises->view(), new_execpromises))
return EINVAL;
if (m_has_execpromises && (new_execpromises & ~m_execpromises))
return EPERM;
m_has_execpromises = true;
m_execpromises = new_execpromises;
}