From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL, SUBJ_OBFU_PUNCT_FEW autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 11465 invoked from network); 9 Oct 2020 20:39:37 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 9 Oct 2020 20:39:37 -0000 Received: (qmail 11468 invoked by uid 550); 9 Oct 2020 20:39:33 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 11450 invoked from network); 9 Oct 2020 20:39:32 -0000 Date: Fri, 9 Oct 2020 16:39:20 -0400 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20201009203919.GA17637@brightrain.aerifal.cx> References: <20201003023703.GT17637@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="+SfteS7bOf3dGlBC" Content-Disposition: inline In-Reply-To: <20201003023703.GT17637@brightrain.aerifal.cx> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] runtime error: initgroups(www-data, 33) failed (5: I/O error) --+SfteS7bOf3dGlBC Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Oct 02, 2020 at 10:37:03PM -0400, Rich Felker wrote: > On Sat, Oct 03, 2020 at 09:06:50AM +0800, Static Php wrote: > > I has this runtime error on Ubuntu 18.04.5 LTS, CPU is AMD EPYC Processor. > > > > Kernel: 5.4.0-49-generic #53~18.04.1-Ubuntu (other kernel also has this > > problem) > > > > more details: https://github.com/richfelker/musl-cross-make/issues/107 > > > > strace: > > > > execve("./a.out", ["./a.out"], 0x7fff12cd26d0 /* 20 vars */) = 0 > > > > > > arch_prctl(ARCH_SET_FS, 0x7ff53bb3b618) = 0 > > > > > > set_tid_address(0x7ff53bb3bbe8) = 40778 > > > > > > socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0) = 3 > > > > > > brk(NULL) = 0x555556f23000 > > > > > > brk(0x555556f25000) = 0x555556f25000 > > > > > > mmap(0x555556f23000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, > > > -1, 0) = 0x555556f23000 > > > > > > mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = > > > 0x7ff53bb39000 > > > > > > connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 24) = 0 > > > > > > sendmsg(3, {msg_name=NULL, msg_namelen=0, > > > msg_iov=[{iov_base="\2\0\0\0\17\0\0\0\t\0\0\0", iov_len=12}, > > > {iov_base="www-data\0", iov_len=9}], msg_iovlen=2, msg_controllen=0, > > > msg_flags=0}, MSG_NOSIGNAL) = 21 > > > > > > readv(3, [{iov_base="\2\0\0\0\1\0\0\0\0\0\0", iov_len=11}, {iov_base="\0", > > > iov_len=1024}], 2) = 12 > > > > > > mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = > > > 0x7ff53bb38000 > > > > > > close(3) = 0 > > > > > > munmap(0x7ff53bb39000, 4096) = 0 > > > > > > munmap(0x7ff53bb38000, 4096) = 0 > > > > > > ioctl(1, TIOCGWINSZ, {ws_row=59, ws_col=225, ws_xpixel=1575, > > > ws_ypixel=826}) = 0 > > > > > > writev(1, [{iov_base="err=-1, errno=5", iov_len=15}, {iov_base="\n", > > > iov_len=1}], 2err=-1, errno=5 > > > > > > ) = 16 > > > > > > exit_group(0) = ? > > > > > > +++ exited with 0 +++ > > > > > Ah, this looks like a bug in musl causing a zero-groups response from > nscd to be interpreted as an error rather than success with no > members: > > if (!fread(nscdbuf, sizeof(*nscdbuf)*resp[INITGRNGRPS], 1, f)) { > if (!ferror(f)) errno = EIO; > goto cleanup; > } > > The problem is that this code was written assuming the fread call > returns 1 on success, but fread has a stupid corner case (which we > used to get wrong) where a zero-length read is required by the > standard to return 0 even though logically it should return nmemb. > > You can work around the problem by adding www-data to a useless dummy > group. I'll prepare a patch for musl, though, and post it here as a > follow-up soon. > > Thanks for the report! I think the attached patch should work, but it's not tested since I dont have an environment with nscd handy. Rich --+SfteS7bOf3dGlBC Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="getgrouplist.diff" diff --git a/src/passwd/getgrouplist.c b/src/passwd/getgrouplist.c index 43e51824..44785e10 100644 --- a/src/passwd/getgrouplist.c +++ b/src/passwd/getgrouplist.c @@ -31,12 +31,13 @@ int getgrouplist(const char *user, gid_t gid, gid_t *groups, int *ngroups) if (resp[INITGRFOUND]) { nscdbuf = calloc(resp[INITGRNGRPS], sizeof(uint32_t)); if (!nscdbuf) goto cleanup; - if (!fread(nscdbuf, sizeof(*nscdbuf)*resp[INITGRNGRPS], 1, f)) { + size_t ngrps = resp[INITGRNGRPS]; + if (ngrps && !fread(nscdbuf, sizeof(*nscdbuf)*ngrps, 1, f)) { if (!ferror(f)) errno = EIO; goto cleanup; } if (swap) { - for (i = 0; i < resp[INITGRNGRPS]; i++) + for (i = 0; i < ngrps; i++) nscdbuf[i] = bswap_32(nscdbuf[i]); } } --+SfteS7bOf3dGlBC--