git: hammer2: Fix a NULL deref in hammer2_chain_lastdrop()

[Aaron LI]

commit fde6d850ed48936eb946997085fd986d2bb3b434
Author: Aaron LI <aly at aaronly.me>
Date:   Tue Oct 13 09:09:55 2026 +0800

    hammer2: Fix a NULL deref in hammer2_chain_lastdrop()
    
    That is the no-parent case, i.e., parent is NULL, so it was an error
    to access 'parent->core.spin'. Simply remove the hammer2_spin_unex()
    call to fix the bug.
    
    This bug was caught by the GCC 12.5 warning:
    
    ```
    In file included from include/machine/atomic.h:7,
                     from /usr/src/sys/sys/systm.h:49,
                     from /usr/src/sys/vfs/hammer2/hammer2_chain.c:57:
    In function 'atomic_add_int',
        inlined from 'spin_unlock_quick' at /usr/src/sys/sys/spinlock2.h:170:2,
        inlined from 'spin_unlock' at /usr/src/sys/sys/spinlock2.h:183:2,
        inlined from 'hammer2_chain_lastdrop' at /usr/src/sys/vfs/hammer2/hammer2_chain.c:654:4,
        inlined from 'hammer2_chain_drop' at /usr/src/sys/vfs/hammer2/hammer2_chain.c:359:13,
        inlined from 'hammer2_chain_drop' at /usr/src/sys/vfs/hammer2/hammer2_chain.c:346:1:
    ./cpu/atomic.h:91:9: warning: array subscript 0 is outside array bounds of 'int[0]' [-Warray-bounds]
       91 |         __asm __volatile(MPLOCKED OP                    \
          |         ^~~~~
    ./cpu/atomic.h:130:1: note: in expansion of macro 'ATOMIC_ASM'
      130 | ATOMIC_ASM(add,      int,   "addl %1,%0", "iq",   v)
          | ^~~~~~~~~~
    ./cpu/atomic.h:91:9: warning: array subscript 0 is outside array bounds of 'int[0]' [-Warray-bounds]
       91 |         __asm __volatile(MPLOCKED OP                    \
          |         ^~~~~
    ./cpu/atomic.h:130:1: note: in expansion of macro 'ATOMIC_ASM'
      130 | ATOMIC_ASM(add,      int,   "addl %1,%0", "iq",   v)
          | ^~~~~~~~~~
    ```

Summary of changes:
 sys/vfs/hammer2/hammer2_chain.c | 1 -
 1 file changed, 1 deletion(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/fde6d850ed48936eb946997085fd986d2bb3b434


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