The code has this: __dup3 (_IO_fileno (result), fd, (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0 ? O_CLOEXEC : 0); That is, there is no error checking for dup3 failure. We should add error checking here.
*** Bug 21398 has been marked as a duplicate of this bug. ***
Since you duped my bug to this one, I would request that the severity be increased. Applications that change for freopen errors end up with extremely hard to debug problems as a result of this.
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, master has been updated via f1a67a2c78601599be51a17250ca02c7d830d79d (commit) from d26db8fbb4787905590f207d56026e915b3bd5b3 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f1a67a2c78601599be51a17250ca02c7d830d79d commit f1a67a2c78601599be51a17250ca02c7d830d79d Author: Adhemerval Zanella <adhemerval.zanella@linaro.org> Date: Fri May 5 11:31:38 2017 -0300 libio: Avoid dup already opened file descriptor [BZ#21393] As described in BZ#21398 (close as dup of 21393) report current freopen implementation fails when one tries to freopen STDIN_FILENO, STDOUT_FILENO, or STDERR_FILENO. Although on bug report the discussion leads to argue if a close followed by a freopen on the standard file is a valid operation, the underlying issue is not really the check for dup3 returned value, but rather calling it if the returned file descriptor is equal as the input one. So for a quality of implementation this patch avoid calling dup3 for the aforementioned case. It also adds a dup3 error case check for the two possible failures, with one being Linux only: EINTR and EBUSY. The EBUSY issue is better explained on this stackoverflow thread [1], but in a short it is due the internal Linux implementation which allows a race condition window for dup2 due the logic dissociation of file descriptor allocation and actual VFS 'install' operation. For both outliers failures all allocated memory is freed and a NULL FILE* is returned. With this patch the example on BZ#21398 is now actually possible (I used as the testcase for the bug report). Checked on x86_64-linux-gnu. [BZ #21393] * libio/freopen.c (freopen): Avoid dup already opened file descriptor and add a check for dup3 failure. * libio/freopen64.c (freopen64): Likewise. * libio/tst-freopen.c (do_test): Rename to do_test_basic and use libsupport. (do_test_bz21398): New test. * manual/stdio.texi (freopen): Add documentation of EBUSY failure. [1] http://stackoverflow.com/questions/23440216/race-condition-when-using-dup2 ----------------------------------------------------------------------- Summary of changes: ChangeLog | 11 +++++ libio/freopen.c | 22 +++++++++-- libio/freopen64.c | 22 +++++++++-- libio/tst-freopen.c | 107 +++++++++++++++++++++++++++------------------------ manual/stdio.texi | 10 ++++- 5 files changed, 113 insertions(+), 59 deletions(-)
Fixed by f1a67a2c78601599be51a17250ca02c7d830d79d.
*** Bug 15589 has been marked as a duplicate of this bug. ***