AsanStackTrace::FastUnwindStack reads wild addresses

[ramosian-glider]

Originally reported on Google Code with ID 44

We've heard about this from external users.
Now I have a repro, thanks to csmith (http://embed.cs.utah.edu/csmith/)

1. Build asan-ified clang
2. run 
  for((i=0; i<16; i++)); do clang -g -O2 small.c -w -o $i.o & done ; wait

clang will eventually crash with 
==25320== ERROR: AddressSanitizer crashed on unknown address 0x7fffc0f10006 (pc 0x000004bc8c10
sp 0x7fffc0f06580 bp 0x7fffc0f067d0 T0)

where the PC is inside AsanStackTrace::FastUnwindStack 

Reported by konstantin.s.serebryany on 2012-03-08 22:00:23

[ramosian-glider]

Reported by konstantin.s.serebryany on 2012-03-08 22:00:50

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- _Attachment: [small.c](https://storage.googleapis.com/google-code-attachments/address-sanitizer/issue-44/comment-1/small.c)_

[ramosian-glider]

With ASAN_OPTIONS=verbosity=1 I can see this: 

==25843== T0: stack [0x7fff5ea70000,0x7fff5f270000) ...
==25843== ERROR: AddressSanitizer crashed on unknown address 0x7fff5f270006 ...

The faulting address is clearly 6 bytes above the stack. 

Reported by konstantin.s.serebryany on 2012-03-08 22:05:47

[ramosian-glider]

Fixed by LLVM r152347

Reported by konstantin.s.serebryany on 2012-03-08 22:34:28

• Status changed: Fixed

[ramosian-glider]

Adding Project:AddressSanitizer as part of GitHub migration.

Reported by ramosian.glider on 2015-07-30 09:12:58

• Labels added: ProjectAddressSanitizer