https://bugs.kde.org/show_bug.cgi?id=511717
Bug ID: 511717
Summary: the 'impossible' happened: Killed by fatal signal
(SIGSEGV)
Classification: Developer tools
Product: valgrind
Version First 3.25.1
Reported In:
Platform: Ubuntu
OS: Linux
Status: REPORTED
Severity: crash
Priority: NOR
Component: memcheck
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
Valgrind sometimes crashes under specific heavy load when stress testing our
Knot DNS project. This seems to be introduced by upgrading from Ubuntu 25.04 to
25.10.
STEPS TO REPRODUCE
1. Install (K)Ubuntu 25.10
2. Download Knot DNS from git https://gitlab.nic.cz/knot/knot-dns , download
the prerequisites (README.md), configure with --enable-static ,
CFLAGS="-gdwarf-4 -O0" , and build
3. Install the prerequisites for testing (tests-extra/requirements.txt) and
run ./runtests.py ctl/concurrent repeatedly
4. Watch for the test to fail and examine
<home>/knottest-last/ctl/concurrent/knot1/valgrind
I do undrestand that actually perform the reproduction is problematic. At least
I can easily trigger the issue repeatedly despite it seems to be somewhat
random in appearance.
OBSERVED RESULT
Snippets from valgrind output. See the complete output in attachment.
...
==237772==
--237772-- VALGRIND INTERNAL ERROR: Valgrind received a signal 11 (SIGSEGV) -
exiting
--237772-- si_code=1; Faulting address: 0x28306000; sp: 0x100f200a68
valgrind: the 'impossible' happened:
Killed by fatal signal
host stacktrace:
==237772== at 0x580470C7: vgPlain_memcpy (m_libcbase.c:692)
==237772== by 0x5809EFC5: valgrind_read_memory (target.c:465)
==237772== by 0x5809C94F: server_main (server.c:1383)
==237772== by 0x580BED33: call_gdbserver (m_gdbserver.c:725)
==237772== by 0x580BFAA1: vgPlain_gdbserver (m_gdbserver.c:792)
==237772== by 0x580A2057: run_thread_for_a_while (scheduler.c:1113)
==237772== by 0x580A368F: vgPlain_scheduler (scheduler.c:1484)
==237772== by 0x58112DB4: thread_wrapper (syswrap-linux.c:102)
==237772== by 0x58112DB4: run_a_thread_NORETURN (syswrap-linux.c:155)
==237772== by 0x581130AE: vgModuleLocal_start_thread_NORETURN
(syswrap-linux.c:339)
==237772== by 0x580B645D: ??? (in
/usr/libexec/valgrind/memcheck-amd64-linux)
==237772== by 0xDEADBEEFDEADBEEE: ???
==237772== by 0xDEADBEEFDEADBEEE: ???
==237772== by 0xDEADBEEFDEADBEEE: ???
sched status:
running_tid=19
Thread 1: status = VgTs_WaitSys syscall 230 (lwpid 237772)
...
Thread 19: status = VgTs_Runnable (lwpid 238690)
==237772== at 0x5AB0490: __gmpn_add_n (in
/usr/lib/x86_64-linux-gnu/libgmp.so.10.5.0)
==237772== by 0x59B4902: _nettle_ecc_dup_jj (in
/usr/lib/x86_64-linux-gnu/libhogweed.so.6.10)
==237772== by 0x59B6EA8: _nettle_ecc_mul_a (in
/usr/lib/x86_64-linux-gnu/libhogweed.so.6.10)
==237772== by 0x59B7CF3: nettle_ecc_ecdsa_verify (in
/usr/lib/x86_64-linux-gnu/libhogweed.so.6.10)
==237772== by 0x59B7ED2: nettle_ecdsa_verify (in
/usr/lib/x86_64-linux-gnu/libhogweed.so.6.10)
==237772== by 0x525F7C1: ??? (in
/usr/lib/x86_64-linux-gnu/libgnutls.so.30.40.3)
==237772== by 0x5195C18: ??? (in
/usr/lib/x86_64-linux-gnu/libgnutls.so.30.40.3)
==237772== by 0x519890E: gnutls_pubkey_verify_data2 (in
/usr/lib/x86_64-linux-gnu/libgnutls.so.30.40.3)
==237772== by 0x40DEEF3: dnssec_sign_verify (sign.c:373)
==237772== by 0x4073E8D: knot_check_signature (rrset-sign.c:415)
==237772== by 0x407B9CD: valid_signature_exists (zone-sign.c:126)
==237772== by 0x407B699: knot_validate_rrsigs (zone-sign.c:313)
==237772== by 0x407DAE2: sign_node_rrsets (zone-sign.c:493)
==237772== by 0x407D8DE: sign_node (zone-sign.c:557)
==237772== by 0x4049043: tree_apply_cb (zone-tree.c:25)
==237772== by 0x4113DE6: apply_nodes (trie.c:988)
==237772== by 0x4113E24: apply_nodes (trie.c:991)
==237772== by 0x4113E24: apply_nodes (trie.c:991)
==237772== by 0x4113E24: apply_nodes (trie.c:991)
==237772== by 0x4113D67: trie_apply (trie.c:1000)
==237772== by 0x4048FB1: zone_tree_apply (zone-tree.c:291)
==237772== by 0x407D7DA: tree_sign_thread (zone-sign.c:563)
==237772== by 0x53E3D63: start_thread (pthread_create.c:448)
==237772== by 0x54771C3: clone (clone.S:100)
client stack range: [0x30CC2000 0x324C3FFF] client SP: 0x324C2FE8
valgrind stack range: [0x100F101000 0x100F200FFF] top usage: 8312 of 1048576
Thread 21: status = VgTs_Init (lwpid 0)
...
EXPECTED RESULT
No crash, either no errors reported, or potentially report memory handling
errors in the tested piece of software (if any, I don't think so)
SOFTWARE/OS VERSIONS
Kubuntu 25.10, Plasma 6.4.5, uname 6.17.0-6-generic #6-Ubuntu SMP
PREEMPT_DYNAMIC Tue Oct 7 13:34:17 UTC 2025 x86_64 GNU/Linux
Using Valgrind-3.25.1-4441567fbe-20250520 and LibVEX
ADDITIONAL INFORMATION
This happens regardless if Knot DNS is built by gcc or clang.
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