[Bug libc/31394] New: clone on sparc might fail with -EFAULT for no valid reason

[sourceware-bugzilla at mkarcher dot dialup.fu-berlin.de]

https://sourceware.org/bugzilla/show_bug.cgi?id=31394

            Bug ID: 31394
           Summary: clone on sparc might fail with -EFAULT for no valid
                    reason
           Product: glibc
           Version: 2.38
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: sourceware-bugzilla at mkarcher dot dialup.fu-berlin.de
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

Created attachment 15373
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15373&action=edit
issue reproducing program.

There seems to be a bug in the sparc and sparc64 linux kernel that results in
spurious -EFAULT errors from clone if %sp is referring to a stack address that
is not (yet) part of the program stack, as the stack is laziliy allocated.

I wrote a reproducer program to demonstrate the the presence of the issue, see
the attached file "more_clone_attack.c". As the reproducing script assumes the
stack bias of 0x7ff, it likely won't work as is on sparc32.

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