Bug#1083095: libc6: SIGSEGV in _dl_open on ARM64 (aarch64) at libc6 2.36-9+deb12u8 called by bash-static 5.2.15-2+b7

[Aurelien Jarno <aurel32@debian.org>]

control: found -1 2.36-9+deb12u8

Hi,

On 2024-10-01 13:25, Jingyuan Liang wrote:
> Package: libc6
> Version: 2.38-7+gl0
> Severity: normal
> X-Debbugs-Cc: jingyuanliang@google.com
> 
> Dear Maintainer,
> 
> The issue happened in a containerized context - the system information extracted below doesn't apply.
> 
> If you speak Docker, the build below is a reproduction of the issue; otherwise, just skip this.
> 
> ```
> FROM debian:bookworm-slim AS bash
> 
> RUN apt-get update && apt-get install -y --no-install-recommends --no-install-suggests bash-static
> 
> FROM gcr.io/distroless/base-debian12@sha256:6ae5fe659f28c6afe9cc2903aebc78a5c6ad3aaa3d9d0369760ac6aaea2529c8
> 
> COPY --from=bash /bin/bash-static /bin/bash
> 
> ENTRYPOINT ["/bin/bash"]
> ```

Thanks for reporting this and for the docker reproducer. This can be 
reproduced in a simpler way by:
- using "compat" in /etc/nsswitch.conf for the passwd database.
- executing bash-static or this simple program compiled statically:

| #include <pwd.h>
| #include <sys/types.h>
| #include <unistd.h>
|
| int main()
| {
|         return getpwuid(getuid()) != NULL;
| }

The issue has been introduced by the following upstream commit:

| commit 24de733967029fd902c34073d2ab25b900887352
| Author: Wilco Dijkstra <wilco.dijkstra@arm.com>
| Date:   Thu Mar 21 16:48:33 2024 +0000
|
|     AArch64: Check kernel version for SVE ifuncs
|    
|     Old Linux kernels disable SVE after every system call.  Calling the
|     SVE-optimized memcpy afterwards will then cause a trap to reenable SVE.
|     As a result, applications with a high use of syscalls may run slower with
|     the SVE memcpy.  This is true for kernels between 4.15.0 and before 6.2.0,
|     except for 5.14.0 which was patched.  Avoid this by checking the kernel
|     version and selecting the SVE ifunc on modern kernels.
|    
|     Parse the kernel version reported by uname() into a 24-bit kernel.major.minor
|     value without calling any library functions.  If uname() is not supported or
|     if the version format is not recognized, assume the kernel is modern.
|    
|     Tested-by: Florian Weimer <fweimer@redhat.com>
|     Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
|     (cherry picked from commit 2e94e2f5d2bf2de124c8ad7da85463355e54ccb2)

A workaround is to use "compat" in /etc/nsswitch.conf if your setup
allows that ("files" being the default). Another one is to rebuild
bash-static against libc6 2.36-9+deb12u8.

I have brought up the issue upstream: 
https://sourceware.org/pipermail/libc-alpha/2024-October/160401.html

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                     http://aurel32.net