Public bug reported:
## Summary
The Ubuntu source-built dotnet-runtime-10.0 (10.0.3-0ubuntu1~25.10.1)
intermittently crashes with "Fatal error. Internal CLR error.
(0x80131506)" during parallel MSBuild operations on Ubuntu 25.10
(questing).
## Root Cause
Ubuntu's source-built .NET 10 links libcoreclr.so against the system
libunwind (libunwind8 1.8.1-0.1ubuntu1):
$ ldd /usr/lib/dotnet/shared/Microsoft.NETCore.App/10.0.3/libcoreclr.so |
grep unwind
libunwind-x86_64.so.8 => /lib/x86_64-linux-gnu/libunwind-x86_64.so.8
libunwind.so.8 => /lib/x86_64-linux-gnu/libunwind.so.8
libunwind 1.8.x has known incompatibilities with .NET's CLR stack
unwinding, specifically in dwarf_find_unwind_table
(Gfind_unwind_table.c) where text segment matching and load_base
calculation changed between 1.6.x and 1.8.x. This breaks unwinding
through ReadyToRun (R2R) pre-compiled assemblies, which are PE-format
files memory-mapped on Linux (not ELF).
Microsoft's official .NET SDK (from dotnet-install.sh) does NOT link to
any external libunwind — libcoreclr.so uses its own built-in DWARF
unwinder and does not crash.
## Crash Chain
1. MSBuild spawns parallel out-of-proc worker nodes via Unix domain sockets
2. Socket.DoConnect throws SocketException (EADDRNOTAVAIL)
3. CLR exception dispatch calls PAL_VirtualUnwind → libunwind's unw_step()
4. unw_step() fails on ReadyToRun frame (PE file, not ELF)
5. SoftwareExceptionFrame::Init calls
EEPOLICY_HANDLE_FATAL_ERROR(COR_E_EXECUTIONENGINE)
6. Process terminates with SIGABRT
## How to Reproduce
On Ubuntu 25.10 with apt-installed dotnet-sdk-10.0:
dotnet new blazor -o /tmp/test-crash
cd /tmp/test-crash
for i in $(seq 1 20); do
dotnet clean -v q 2>/dev/null
dotnet build 2>&1 || echo "CRASH on iteration $i"
done
The crash occurs intermittently (~1 in 5-10 clean builds). Using -m:1
avoids it.
## Environment
- Ubuntu 25.10 (questing), kernel 6.17.0-14-generic
- dotnet-runtime-10.0: 10.0.3-0ubuntu1~25.10.1
- dotnet-sdk-10.0: 10.0.103-0ubuntu1~25.10.1
- libunwind8: 1.8.1-0.1ubuntu1
- Architecture: amd64
## Workaround
Install Microsoft's official .NET SDK via dotnet-install.sh instead of
Ubuntu's apt package. Microsoft's build does not link to system
libunwind.
## Related Issues
- https://github.com/dotnet/runtime/issues/97343 (libunwind 1.8.0 broke remote
unwind)
- https://github.com/dotnet/runtime/issues/111855 (createdump crashes with
system libunwind 1.8.0)
- https://bugs.launchpad.net/ubuntu/+source/dotnet7/+bug/2065178 (same class of
issue on dotnet7)
## Suggested Fix
Either:
1. Patch dotnet10 source-build to bundle its own libunwind (like Microsoft's
SDK), OR
2. Patch libunwind 1.8.1 with upstream fixes for .NET compatibility
** Affects: dotnet10 (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2143357
Title:
dotnet-runtime-10.0 crashes intermittently (0x80131506) due to system
libunwind 1.8.1 incompatibility
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