From b3a810d0d3d5c6ce7ddfb61321cd7971808ca703 Mon Sep 17 00:00:00 2001 From: Stefan Liebler Date: Tue, 17 May 2016 10:45:48 +0200 Subject: [PATCH] Fix tst-cancel17/tst-cancelx17, which sometimes segfaults while exiting. The testcase tst-cancel[x]17 ends sometimes with a segmentation fault. This happens in one of 10000 cases. Then the real testcase has already exited with success and returned from do_test(). The segmentation fault occurs after returning from main in _dl_fini(). In those cases, the aio_read(&a) was not canceled because the read request was already in progress. In the meanwhile aio_write(ap) wrote something to the pipe and the read request is able to read the requested byte. The read request hasn't finished before returning from do_test(). After it finishes, it writes the return value and error code from the read syscall to the struct aiocb a, which lies on the stack of do_test. The stack of the subsequent function call of _dl_fini or _dl_sort_fini, which is inlined in _dl_fini is corrupted. In case of S390, it reads a zero and decrements it by 1: unsigned int k = nmaps - 1; struct link_map **runp = maps[k]->l_initfini; The load from unmapped memory leads to the segmentation fault. The stack corruption also happens on other architectures. I saw them e.g. on x86 and ppc, too. This patch adds an aio_suspend call to ensure, that the read request is finished before returning from do_test(). ChangeLog: * nptl/tst-cancel17.c (do_test): Wait for finishing aio_read(&a). --- ChangeLog | 4 ++++ nptl/tst-cancel17.c | 16 ++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/ChangeLog b/ChangeLog index a191caff00..95de597034 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,7 @@ +2016-05-17 Stefan Liebler + + * nptl/tst-cancel17.c (do_test): Wait for finishing aio_read(&a). + 2016-05-13 Florian Weimer Fix race condition in tst-mallocfork2, use fewer resources. diff --git a/nptl/tst-cancel17.c b/nptl/tst-cancel17.c index fb89292070..eedd28e792 100644 --- a/nptl/tst-cancel17.c +++ b/nptl/tst-cancel17.c @@ -333,6 +333,22 @@ do_test (void) puts ("early cancellation succeeded"); + if (ap == &a2) + { + /* The aio_read(&a) was not canceled because the read request was + already in progress. In the meanwhile aio_write(ap) wrote something + to the pipe and the read request either has already been finished or + is able to read the requested byte. + Wait for the read request before returning from this function because + the return value and error code from the read syscall will be written + to the struct aiocb a, which lies on the stack of this function. + Otherwise the stack from subsequent function calls - e.g. _dl_fini - + will be corrupted, which can lead to undefined behaviour like a + segmentation fault. */ + const struct aiocb *l[1] = { &a }; + TEMP_FAILURE_RETRY (aio_suspend(l, 1, NULL)); + } + return 0; }