On 8/21/2026 10:09 PM, sashiko-bot@kernel.org wrote:
When duplicating a process' virtual memory mappings also duplicate all
of its registered .eh_frame_hdr sections stored in the per-mm maple tree
to enable stacktracing using eh_frame of the child process.
quoted
diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c
quoted
@@ -1501,6 +1501,54 @@ int eh_frame_remove_section(unsigned long eh_frame_hdr_start)
return 0;
}
+static void __eh_frame_dup_section(struct eh_frame_section *sec,
+ struct eh_frame_section *oldsec)
+{
[ ... ]
quoted
+}
+
+int eh_frame_dup_mm(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+ struct eh_frame_section *sec, *oldsec;
+ unsigned long index = 0;
+ int ret;
+
+ guard(srcu)(&eh_frame_srcu);
[Severity: Medium]
Is it acceptable to mix goto-based error handling with guard() in the same
function? The cleanup guidelines suggest converting all resources to
scope-based cleanup or none to avoid confusing ownership semantics.
I think it is acceptable.
quoted
+
+ mt_for_each(&oldmm->eh_frame_mt, oldsec, index, ULONG_MAX) {
[Severity: High]
Does this unconditionally duplicate all eh_frame sections from the parent
without checking if the underlying VMA was actually copied during the fork?
If a process sets a region to VM_DONTCOPY or VM_WIPEONFORK before forking,
the child won't inherit the VMA, but it appears it will still inherit
the eh_frame section here. If the child process later maps new executable
code at the same address, could the unwinder use the parent's stale rules?
Steven, could you please advise?
quoted
+ sec = kzalloc(sizeof(*sec), GFP_KERNEL_ACCOUNT);
+ if (!sec)
+ return -ENOMEM;
+
+ __eh_frame_dup_section(sec, oldsec);
+
+ ret = mtree_insert_range(&mm->eh_frame_mt,
+ sec->text_start,
+ sec->text_end - 1,
+ sec, GFP_KERNEL_ACCOUNT);
+ if (ret)
+ goto err_free;
+ }
+
+ return 0;
+
+err_free:
+ free_section(sec);
+ return ret;
+}
Thanks and regards,
Jens
--
Jens Remus
Linux on Z Development (D3303)
jremus@de.ibm.com / jremus@linux.ibm.com
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