[Bug 609290] [NEW] Critical bug in memcpy-ssse3-rep.S

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Hello.
I found a terrible bug in memory copy routine (eglibc-2.11.1/sysdeps/i386/i686/multiarch/memcpy-ssse3-rep.S and memcpy-ssse3.S). Here is the code

    movl    LEN(%esp), %ecx
    movl    SRC(%esp), %eax
    movl    DEST(%esp), %edx
......
L(fwd_write_less32bytes):
#ifndef USE_AS_MEMMOVE
    cmp    %dl, %al     -----<<<<< BUG !!!
    jb    L(bk_write)

Assume, that I have an array of char AR and I want move data from AR[10] to AR[0] with length 47. Data should be copied in forward direction. Problem is when AR[10] overlaps 255 bytes boundary. For example address of AR[0] is 0x000000F8 (EDX) and address of AR[10] is 0x00000102 (EAX) then cmp %dl,%al return AL as smaller then DL and the data are copied in reverse direction that causes data corruption.
In reality it will cause problems on Ubuntu 10.04 mod_ssl in Apache with last updates installed (libc6:  Installed: 2.11.1-0ubuntu7.2), which are sometimes unable to process the HTTP header because of malformed data, but may cause other unexpected behavior (bug #595116, bug #595855, bug #589611 and maybe others).

I don't know if only this two files is affected by this bug.

See GDB snapshot in attachment

  Regards
     Jiri Engelthaler

** Affects: apache2 (Ubuntu)
     Importance: Undecided
         Status: New

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Critical bug in memcpy-ssse3-rep.S
https://bugs.launchpad.net/bugs/609290
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