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From: "adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug libc/30737] fdopendir() is not robust - returns bogus DIR* instead of flagging an error Date: Tue, 08 Aug 2023 20:48:48 +0000 [thread overview] Message-ID: <bug-30737-131-DzogGt0hHD@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-30737-131@http.sourceware.org/bugzilla/> https://sourceware.org/bugzilla/show_bug.cgi?id=30737 Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |adhemerval.zanella at linaro dot o | |rg --- Comment #3 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> --- (In reply to Mark Galeck from comment #0) > First, dislclaimer: I checked this issue is present on the latest Ubuntu > distribution, which has glibc version 2.35, not the latest stable 2.38. I > was able to build 2.38 locally, but I am not able to force Ubuntu to accept > it for linking to the sample program, or to upgrade the installed glibc 2.35 > to 2.38. > > If you know how to test the sample program with 2.38, please let me know, > and I will do so and I will remove this report if it does not reproduce with > glibc 2.38. > --------------------------- > > Here is the SSCCE > 'foobar.c' > > (which I obtained by necessary modifications to the sample code in man7 > entry for fdopendir() ) : > > > #define _GNU_SOURCE > > #include <stdio.h> > #include <dirent.h> > #include <fcntl.h> > #include <stdlib.h> > #include <string.h> > > int > main(int argc, char* argv[]) > { > DIR* d; > struct dirent* dp; > int dfd; > > if ((d = fdopendir(open("./dir", O_RDONLY | O_PATH | O_DIRECTORY))) == > NULL) { > fprintf(stderr, "Cannot open directory\n"); > exit(1); > } > > while ((dp = readdir(d)) != NULL) { > if (!strcmp(dp->d_name, ".")) > continue; > if (!strcmp(dp->d_name, "..")) > continue; > printf("d_name %s\n", dp->d_name); > } > return 0; > } > > ------------------------- > Here is a script to show the problem: > > $ mkdir dir > $ touch dir/file > $ gcc -lc foobar.c > $ ./a.out > $ > > When called on a descriptor opened with O_PATH , fdopendir() succeeds > happily, but then, readdir() reports nothing! But readdir *does* report it, if you set errno as 0 prior calling, you will see that EBADF is correctly set (from getdents64). > > So the DIR* returned from fdopendir() is useless, but fdopendir() returns > it, instead of NULL and setting errno to EBADF , as it should INHO > Although POSIX defines fdopendir EBADF for file descriptors not open for reading, O_PATH is a Linux extension, and standard-wise not failing with it is still conformant. However, I agree this is QoI to fail if the file descriptor is opened with O_PATH (it fails early and Linux fdopendir already call fcntl, so it is a free check). > > If I remove | O_PATH from the above sample code, I get the expected result: > > $gcc -lc foobar.c > $ ./a.out > d_name file -- You are receiving this mail because: You are on the CC list for the bug.
next prev parent reply other threads:[~2023-08-08 20:48 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-08-08 15:52 [Bug libc/30737] New: " markgaleck at gmail dot com 2023-08-08 16:26 ` [Bug libc/30737] " markgaleck at gmail dot com 2023-08-08 16:27 ` markgaleck at gmail dot com 2023-08-08 20:48 ` adhemerval.zanella at linaro dot org [this message] 2023-08-08 23:35 ` markgaleck at gmail dot com 2023-08-10 11:04 ` adhemerval.zanella at linaro dot org 2023-11-30 16:38 ` adhemerval.zanella at linaro dot org
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