hi, i've noticed that some 3rd-party tk-based application causing a tigervnc-server-1.9.0-4.fc30.x86_64 server crash. as you can see the tigervnc passes to memcpy negatice __len value. (gdb) fr 1 #1 0x000056043df40e79 in memcpy (__len=18446744073709551528, __src=<optimized out>, __dest=<optimized out>) at /usr/include/bits/string_fortified.h:34 warning: Source file is more recent than executable. 34 return __builtin___memcpy_chk (__dest, __src, __len, __bos0 (__dest)); (gdb) p/x __len $1 = 0xffffffffffffffa8 % gdb /usr/bin/Xvnc --core core.8583 GNU gdb (GDB) Fedora 8.3-6.fc30 (...) Reading symbols from /usr/bin/Xvnc... Reading symbols from /usr/lib/debug/usr/bin/Xvnc-1.9.0-4.fc30.x86_64.debug... (...) Core was generated by `/usr/bin/Xvnc'. Program terminated with signal SIGSEGV, Segmentation fault. #0 __memmove_avx_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:534 534 VMOVU -(VEC_SIZE * 2)(%rcx), %VEC(2) [Current thread is 1 (Thread 0x7fc91ca2cb40 (LWP 8583))] (gdb) bt #0 __memmove_avx_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:534 #1 0x000056043df40e79 in memcpy (__len=18446744073709551528, __src=<optimized out>, __dest=<optimized out>) at /usr/include/bits/string_fortified.h:34 #2 fbBlt (srcLine=<optimized out>, srcStride=srcStride@entry=1004, srcX=<optimized out>, dstLine=<optimized out>, dstStride=dstStride@entry=1004, dstX=<optimized out>, width=-704, height=113, alu=3, pm=4294967295, bpp=32, reverse=1, upsidedown=0) at fbblt.c:82 #3 0x000056043df4e13d in fbCopyNtoN (pSrcDrawable=pSrcDrawable@entry=0x56044031c970, pDstDrawable=pDstDrawable@entry=0x56044031c970, pGC=pGC@entry=0x56043e5a3f20, pbox=0x7ffd783e89c0, nbox=<optimized out>, nbox@entry=1, dx=dx@entry=-218, dy=0, reverse=1, upsidedown=0, bitplane=0, closure=0x0) at fbcopy.c:69 #4 0x000056043e099993 in miCopyRegion (pSrcDrawable=pSrcDrawable@entry=0x56044031c970, pDstDrawable=pDstDrawable@entry=0x56044031c970, pGC=pGC@entry=0x56043e5a3f20, pDstRegion=pDstRegion@entry=0x7ffd783e89c0, dx=dx@entry=-218, dy=dy@entry=0, copyProc=0x56043df4def0 <fbCopyNtoN>, bitPlane=0, closure=0x0) at micopy.c:121 #5 0x000056043e09a0f6 in miDoCopy (pSrcDrawable=0x56044031c970, pDstDrawable=0x56044031c970, pGC=0x56043e5a3f20, xIn=552, yIn=39, widthSrc=65514, heightSrc=113, xOut=770, yOut=39, copyProc=0x56043df4def0 <fbCopyNtoN>, bitPlane=0, closure=0x0) at micopy.c:296 #6 0x000056043df4e726 in fbCopyArea (pSrcDrawable=<optimized out>, pDstDrawable=<optimized out>, pGC=<optimized out>, xIn=<optimized out>, yIn=<optimized out>, widthSrc=<optimized out>, heightSrc=113, xOut=770, yOut=39) at fbcopy.c:244 #7 0x000056043dfc3ef6 in damageCopyArea (pSrc=0x56044031c970, pDst=0x56044031c970, pGC=0x56043e5a3f20, srcx=<optimized out>, srcy=<optimized out>, width=65514, height=113, dstx=770, dsty=39) at damage.c:775 #8 0x000056043e05b55d in ProcCopyArea (client=0x56043e63b420) at dispatch.c:1721 #9 0x000056043e05fabb in Dispatch () at dispatch.c:478 #10 0x000056043e063b04 in dix_main (argc=17, argv=0x7ffd783e8cd8, envp=<optimized out>) at main.c:276 #11 0x00007fc91d1c2f33 in __libc_start_main (main=0x56043df3a790 <main>, argc=17, argv=0x7ffd783e8cd8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd783e8cc8) at ../csu/libc-start.c:308 #12 0x000056043df3be7e in _start () at dispatch.c:357
Upstream says it's an issue in Xorg server. Upstream bug: https://github.com/TigerVNC/tigervnc/issues/853
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