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From: "renegat.nospam at gmail dot com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug libc/12981] race in aio handle_fildes_io corrupts user memory Date: Tue, 19 Jul 2011 06:15:00 -0000 [thread overview] Message-ID: <bug-12981-131-U6J6cLmTxq@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-12981-131@http.sourceware.org/bugzilla/> http://sourceware.org/bugzilla/show_bug.cgi?id=12981 renegat.nospam at gmail dot com changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |renegat.nospam at gmail dot | |com --- Comment #1 from renegat.nospam at gmail dot com 2011-07-19 06:14:12 UTC --- The call to __aio_notify() should not be skipped, because even if the request itself requires no notification, it could be associated with a waitlist that is processed within __aio_notify(), if the request is part of an asynchronous 'lio_listio' operation. Suggestions to fix this bug: - add additional parameter 'int error_code' to interface of __aio_notify() - at start of __aio_notify(): 1. save the value of field 'aio_sigevent.sigev_notify' to new local variable 'int notify' 2. insert a read memory barrier afterwards 3. assign aiocb field '__error_code' to value of parameter error_code 4. skip call to __aio_notify_only() if notify is SIGEV_NONE - change the (only two) calls to __aio_notify() to pass the error code and remove previous assignment or - add new field 'int sigev_notify' to 'struct requestlist' - within __aio_enqueue_request(): assign it with value of 'aio_sigevent.sigev_notify' - within __aio_notify(): skip call to __aio_notify_only() if req->sigev_notify is SIGEV_NONE There is also a race condition (only minor bug) within aio_cancel(): because a user thread different from that who called aio_cancel() may poll aio_error() and as soon as the return value is ECANCELED this thread can call aio_return(), which may return a value other than -1 as required by POSIX standard. 'sysdeps/pthread/aio_cancel.c': int aio_cancel (fildes, aiocbp) int fildes; struct aiocb *aiocbp; { ... req->aiocbp->aiocb.__error_code = ECANCELED; req->aiocbp->aiocb.__return_value = -1; __aio_notify (req); ... } Bug fixes here: If the first bug fix is chosen above it will fix this bug automatically by moving the assignment of '__error_code' within __aio_notify(), in the other case: swap the two assignments and insert a write memory barrier in-between. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
next prev parent reply other threads:[~2011-07-19 6:15 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-07-11 15:40 [Bug libc/12981] New: " dlbulk-sourcesredhat at yahoo dot com 2011-07-12 20:58 ` [Bug libc/12981] " ppluzhnikov at google dot com 2011-07-19 6:15 ` renegat.nospam at gmail dot com [this message] 2012-12-19 10:41 ` schwab@linux-m68k.org 2014-06-27 12:56 ` fweimer at redhat dot com 2015-08-27 22:06 ` [Bug librt/12981] " jsm28 at gcc dot gnu.org
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