Re: [musl] runtime error: initgroups(www-data, 33) failed (5: I/O error)

[Rich Felker <dalias@libc.org>]

On Sun, Oct 25, 2020 at 02:03:07PM +0800, Static Php wrote:
> I am not sure which step I made wrong, but I still get this error.
> 
> 1. make clean
> 2. make musl-1.2.1
> 3. patch -p1 < ../patches/musl-1.2.0/0002-group.diff
> 4. make all -j8
> 5. sudo make install
> 
> then I relink my php, test at  old server and get the same result.

It's not clear which directories you're running those commands in. It
should just be sufficient to put the patch in patches/musl-1.2.1 (note
you have 1.2.0 and 1.2.1 mismatched above) and re-run mcm from scratch
(or just rm -rf the obj_musl directory under build/local/$(TARGET) and
re-run an incremental make; no need to build gcc again.

Rich


> On Sat, Oct 10, 2020 at 4:39 AM Rich Felker <dalias@libc.org> wrote:
> 
> > 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
> >