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c18n: Improve detection of interrupted compartment #2220

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c18n: Improve detection of interrupted compartment #2220

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58 changes: 34 additions & 24 deletions libexec/rtld-elf/rtld_c18n.c
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Original file line number Diff line number Diff line change
Expand Up @@ -762,6 +762,7 @@
*/
static char dummy_stk;
sp = &dummy_stk;
set_untrusted_stk(sp);
#endif
size = cheri_getlen(sp);
assert(size > 0);
Expand Down Expand Up @@ -1733,6 +1734,13 @@
thr_thread_start(curthread);
}

static bool
identify_untrusted_stk(void *canonical, void *untrusted)
{
canonical = cheri_clearperm(canonical, CHERI_PERM_SW_VMEM);
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return (cheri_is_subset(untrusted, canonical));
}

void
_rtld_thr_exit(long *state)
{
Expand Down Expand Up @@ -1762,7 +1770,8 @@
data = &table->meta->compart_stk[i];
if (data->size == 0)
continue;
if (!cheri_is_subset(data->begin, table->entries[i].stack)) {
if (!identify_untrusted_stk(
data->begin, table->entries[i].stack)) {
rtld_fdprintf(STDERR_FILENO,
"c18n: Untrusted stack %#p of %s is not derived "
"from %#p\n", table->entries[i].stack,
Expand Down Expand Up @@ -1896,22 +1905,22 @@
intr_idx = tf->callee;
intr = index_to_cid(intr_idx);
if (intr < table->meta->capacity &&
table->meta->compart_stk[intr].size > 0) {
if (cheri_is_subset(table->meta->compart_stk[intr].begin, nsp))
goto found;
/*
* If the interrupt occured at a point in the trampoline while a
* tail-call is taking place, where the callee has been updated
* but the callee's stack has not been installed yet, nsp would
* refer to the stack top of the compartment identified as the
* caller in a partially constructed frame above the topmost
* frame.
*/
intr_idx = tf[-1].caller;
intr = index_to_cid(intr_idx);
if (cheri_is_subset(table->meta->compart_stk[intr].begin, nsp))
goto found_trusted;
}
table->meta->compart_stk[intr].size > 0 &&
identify_untrusted_stk(table->meta->compart_stk[intr].begin, nsp))
goto found;
/*
* If the interrupt occured at a point in the trampoline while a
* tail-call is taking place, where the callee has been updated but the
* callee's stack has not been installed yet, nsp would refer to the
* stack top of the compartment identified as the caller in a partially
* constructed frame above the topmost frame.
*/
intr_idx = tf[-1].caller;
intr = index_to_cid(intr_idx);
if (intr < table->meta->capacity &&
table->meta->compart_stk[intr].size > 0 &&
identify_untrusted_stk(table->meta->compart_stk[intr].begin, nsp))
goto found_trusted;
/*
* If the interrupt occurred at a point in the trampoline where a new
* frame has been pushed but the callee's stack has not been installed
Expand All @@ -1928,7 +1937,7 @@
*/
intr_idx = tf->caller;
intr = index_to_cid(intr_idx);
if (cheri_is_subset(table->meta->compart_stk[intr].begin, nsp))
if (identify_untrusted_stk(table->meta->compart_stk[intr].begin, nsp))
goto found_trusted;
/*
* Lazy binding, thread-local storage, and stack resolution all involve
Expand All @@ -1937,11 +1946,8 @@
*/
intr_idx = cid_to_index(RTLD_COMPART_ID);
intr = RTLD_COMPART_ID;
if (cheri_is_subset(table->meta->compart_stk[intr].begin, nsp))
if (identify_untrusted_stk(table->meta->compart_stk[intr].begin, nsp))
goto found_trusted;
#ifndef __ARM_MORELLO_PURECAP_BENCHMARK_ABI
found_failed:
#endif
rtld_fdprintf(STDERR_FILENO,
"c18n: Cannot resolve inconsistent untrusted stack %#p. "
"Please file a bug report!\n", nsp);
Expand All @@ -1953,11 +1959,15 @@
* running code in Executive mode. This performs a quick sanity check.
*/
if ((cheri_getperm(ucp->uc_mcontext.mc_capregs.cap_elr) &
CHERI_PERM_EXECUTIVE) == 0)
goto found_failed;
CHERI_PERM_EXECUTIVE) == 0) {
rtld_fdprintf(STDERR_FILENO,
"c18n: Cannot resolve inconsistent untrusted stack %#p in "
"Restricted Mode. Please file a bug report!\n", nsp);
abort();
}
#endif
found:

Check warning on line 1970 in libexec/rtld-elf/rtld_c18n.c

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Missing Signed-off-by: line
/*
* Emulate a compartment transition from the interrupted compartment to
* RTLD.
Expand Down
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