** Description changed: + Impact + ------ + + Users might face a segmentation fault crash while executing 'pstree'. Backporting this fix will avoid 'pstree' breakage in our users' systems under + certain circumstances. + + This is a timing issue where if the 'get_threadname' function is called and + during its execution the target thread is deleted, it tries to close a file + that does not exist anymore. This happens because of a coding issue, 'pstree' + invokes fclose function even if the fopen function call returns NULL. The + proposed patch fixes this issue simply moving the fclose function call three + lines up, inside of a conditional block which guarantees that the file was + properly open (the pointer to the file is not NULL). + + This bug was introduced in upstream version 22.21 and fixed in version 23.0, + which means that Xenial is the only affected Ubuntu release: + + $ rmadison psmisc + psmisc | 22.15-2ubuntu1 | precise | source, amd64, armel, armhf, i386, powerpc + psmisc | 22.15-2ubuntu1.2 | precise-updates | source, amd64, armel, armhf, i386, powerpc + psmisc | 22.20-1ubuntu2 | trusty | source, amd64, arm64, armhf, i386, powerpc, ppc64el + psmisc | 22.21-2.1build1 | xenial | source, amd64, arm64, armhf, i386, powerpc, ppc64el, s390x + psmisc | 23.1-1 | bionic | source, amd64, arm64, armhf, i386, ppc64el, s390x + psmisc | 23.1-1ubuntu0.1 | bionic-updates | source, amd64, arm64, armhf, i386, ppc64el, s390x + psmisc | 23.2-1 | disco | source, amd64, arm64, armhf, i386, ppc64el, s390x + psmisc | 23.2-1 | eoan | source, amd64, arm64, armhf, i386, ppc64el, s390x + + + Test Case + --------- + + Since timing is an important factor for this issue, it is not easy to + reproduce via a test case. This bug might pop up in any 'pstree' call + regardless of the parameters passed to it. When it happens the user will + be able to notice the segmentation fault immediately in the standard + output. Below is the stack trace generated by the user who reported this + bug on Debian : + + Core was generated by `pstree'. + Program terminated with signal SIGSEGV, Segmentation fault. + #0 _IO_new_fclose (fp=0x0) at iofclose.c:54 + 54 iofclose.c: No such file or directory. + (gdb) bt + #0 _IO_new_fclose (fp=0x0) at iofclose.c:54 + #1 0x00000000004037be in ?? () + #2 0x0000000000401a43 in ?? () + #3 0x00007f577c553b45 in __libc_start_main (main=0x401670, argc=1, + argv=0x7ffeb6139328, init=<optimized out>, fini=<optimized out>, + rtld_fini=<optimized out>, stack_end=0x7ffeb6139318) at libc-start.c:287 + #4 0x0000000000401e8d in ?? () + + + However, as presented in the last section it is an easily identifiable error + in the code, and the fix is quite straightforward. + +  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815902 + + + Regression Potential + -------------------- + + There is a potential problem since the bug was not reproducible in our + side. Timing issues are hard to reproduce in general, so there might be + another case(s) where this kind of situation can happen. The fix impacts + only the 'pstree' utility, so any problem with other binaries provided + by psmisc is not related to this update. + + + [Original message] + As per https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815902 Perhaps Xenial needs to be upgraded to use 22.22??
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