multiple: fix lock management bugs and improve error handling

[feizaizheli]

This commit fixes several critical bugs across multiple packages:

1. syscall: Fix incorrect defer usage in forkpipe2.go lock management

   • acquireForkLock: Remove defer that causes double unlock when hasWaitingReaders returns true. The deferred Unlock() would execute after manual unlock/relock sequence, causing undefined behavior.
   • releaseForkLock: Unlock before panic to prevent deadlock when detecting negative forking count.

2. encoding/json: Add defensive bounds checking in stream.go

   • Token(): Add len(tokenStack) == 0 check before accessing tokenStack[len(tokenStack)-1] for both ']' and '}' delimiters.
   • Prevents potential panic on malformed or concurrent access.

3. syscall: Replace panic with error return in Accept4 functions

   • syscall_freebsd.go, syscall_netbsd.go, syscall_openbsd.go:
   • Change panic("RawSockaddrAny too small") to return EINVAL error.
   • Allows graceful error handling instead of crashing the program.

These fixes improve robustness in concurrent scenarios and abnormal input handling, following Go's error handling best practices.

Fixes: Lock management issues in fork operations
Fixes: Potential array bounds violations in JSON parsing
Fixes: Inappropriate panic usage in syscall package

Change-Id: Ia1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0

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[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

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[gopherbot]

Message from Keith Randall:

Patch Set 2:

(3 comments)

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