[Bug 212708] aio cross-process memory corruption

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212708

            Bug ID: 212708
           Summary: aio cross-process memory corruption
           Product: Base System
           Version: 11.0-STABLE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: slw at zxy.spb.ru
                CC: freebsd-amd64 at FreeBSD.org
                CC: freebsd-amd64 at FreeBSD.org

I am use nginx with AIO and AIO from one nginx process corrupt memory
from other nginx process. Yes, this is cross-process memory
corruption.

Last case, core dumped proccess with pid 1060 at 15:45:14.
Corruped memory at 0x860697000.
I am know about good memory at 0x86067f800.
Dumping (form core) this region to file and analyze by hexdump I am
found start of corrupt region -- offset 0000c8c0 from 0x86067f800.
0x86067f800+0xc8c0 = 0x86068c0c0

I am preliminary enabled debuggin of AIO started operation to nginx
error log (memory address, file name, offset and size of transfer).

grep -i 86068c0c0 error.log near 15:45:14 give target file.
grep ce949665cbcd.hls error.log near 15:45:14 give next result:

2016/09/15 15:45:13 [notice] 1055#0: *11659936 AIO_RD 000000082065DB60 start
000000086068C0C0 561b0   2646736 ce949665cbcd.hls
2016/09/15 15:45:14 [notice] 1060#0: *10998125 AIO_RD 000000081F1FFB60 start
000000086FF2C0C0 6cdf0 140016832 ce949665cbcd.hls
2016/09/15 15:45:14 [notice] 1055#0: *11659936 AIO_RD 00000008216B6B60 start
000000086472B7C0 7ff70   2999424 ce949665cbcd.hls

0x860697000-0x86068c0c0 = 0xaf40

from memory dump:
0000af00  5c 81 4d 7c 0b b6 81 f2  c8 a5 df 94 08 43 c1 08  |\.M|.........C..|
0000af10  74 00 57 55 5f 15 11 b1  00 d5 29 6a 4e d2 fd fb  |t.WU_.....)jN...|
0000af20  49 d1 fd 98 49 58 b7 66  c2 c9 64 67 30 05 06 c0  |I...IX.f..dg0...|
0000af30  0e b2 64 fa b7 9f 69 69  fc cd 91 82 83 ba c3 f2  |..d...ii........|
0000af40  b7 34 eb 8e 0e 88 40 60  1b a8 71 7a 12 15 26 d3  |.4....@`..qz..&.|
0000af50  7f 3e 80 e9 74 96 30 24  cb 82 88 8a ea e0 45 10  |.>..t.0$......E.|
0000af60  e5 75 b2 f7 5b 7c 83 fa  95 a9 09 80 0a 8c fd a9  |.u..[|..........|
0000af70  ef 30 f6 68 9c b2 3f ae  2e e5 21 79 78 8b 34 36  |.0.h..?...!yx.46|
0000af80  c6 55 16 a2 47 00 ca 13  9c 8e 2c 6b eb c7 4f 51  |.U..G.....,k..OQ|
0000af90  81 80 71 f3 a5 9a 5f 40  54 9c f1 f9 ba 81 b2 82  |..q..._ at T.......|

from disk file (offset from 2646736):
0000af00  5c 81 4d 7c 0b b6 81 f2  c8 a5 df 94 08 43 c1 08  |\.M|.........C..|
0000af10  74 00 57 55 5f 15 11 b1  00 d5 29 6a 4e d2 fd fb  |t.WU_.....)jN...|
0000af20  49 d1 fd 98 49 58 b7 66  c2 c9 64 67 30 05 06 c0  |I...IX.f..dg0...|
0000af30  0e b2 64 fa b7 9f 69 69  fc cd 91 82 83 ba c3 f2  |..d...ii........|
0000af40  b7 34 eb 8e 0e 88 40 60  1b a8 71 7a 12 15 26 d3  |.4....@`..qz..&.|
0000af50  7f 3e 80 e9 74 96 30 24  cb 82 88 8a ea e0 45 10  |.>..t.0$......E.|
0000af60  e5 75 b2 f7 5b 7c 83 fa  95 a9 09 80 0a 8c fd a9  |.u..[|..........|
0000af70  ef 30 f6 68 9c b2 3f ae  2e e5 21 79 78 8b 34 36  |.0.h..?...!yx.46|
0000af80  c6 55 16 a2 47 00 ca 13  9c 8e 2c 6b eb c7 4f 51  |.U..G.....,k..OQ|
0000af90  81 80 71 f3 a5 9a 5f 40  54 9c f1 f9 ba 81 b2 82  |..q..._ at T.......|

Bingo!
aio read file by process 1055 placed to same memory address as requested but in
memory space of process 1060!

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