Re: bug in fchownat in n32 and 64 ABIs

[David Daney]

On 10/27/2011 12:26 PM, David Daney wrote:
> On 10/27/2011 12:07 PM, Bruno Haible wrote:
> > Hi Linux/MIPS folks,
> >
> > Found this bug by running the gnulib POSIX test suite: In the fchownat()
> > call, an uid_t or gid_t of value (uid_t)-1 or (gid_t)-1 means no change.
> > See<http://pubs.opengroup.org/onlinepubs/9699919799/functions/fchownat.html>.
> > This value is correctly recognized on all Unices, _except_ Linux/MIPS
> > in n32 and 64 ABIs.
> [...]
> > $ gcc -Wall -mabi=64 foo.c
> > $ ./a.out ; echo $?
> > fchownat: Operation not permitted
> > fchownat: Operation not permitted
> > fchownat: Operation not permitted
> > 14
> > $ gcc -Wall -mabi=n32 foo.c
> > $ ./a.out ; echo $?
> > fchownat: Operation not permitted
> > fchownat: Operation not permitted
> > fchownat: Operation not permitted
> > 14
> > $ gcc -Wall -mabi=32 foo.c
> > $ ./a.out ; echo $?
> >
> > Other relevant data:
> > - kernel version is 2.6.27.1
> > - glibc version is 2.7
> > - gcc version is 4.3.2 (Debian).
>
> Debian doesn't support 64-bit ABIs, so this list is incomplete.  Where
> did you get your 64-bit libc ?
>
> > 'strace' of this program shows that the system call that returns with -1/EPERM
> > is a call to SYS_6254 (in n32 ABI) or SYS_5250 (in 64 ABI).
> Can you get strace -- version 4.5.20 or later and build it for the
> corresponding ABI?  That should properly decode the relevant syscalls.
>
> Once you have that, you might post the strace output.
>
> In the mean time I might give it a try with my 2.9 glibc on a 2.6.32.27
> kernels.

n64 seems to work for me.  Witness:

# strace ./fchownat-test
execve("./fchownat-test", ["./fchownat-test"], [/* 6 vars */]) = 0
brk(0)                                  = 0x12a14b000
uname({sys="Linux", node="(none)", ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) 
= 0x5558e31000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or 
directory)
open("/etc/ld.so.cache", O_RDONLY)      = -1 ENOENT (No such file or 
directory)
open("/lib64/tls/octeon/libc.so.6", O_RDONLY) = -1 ENOENT (No such file 
or directory)
stat("/lib64/tls/octeon", 0xffffc9db70) = -1 ENOENT (No such file or 
directory)
open("/lib64/tls/libc.so.6", O_RDONLY)  = -1 ENOENT (No such file or 
directory)
stat("/lib64/tls", 0xffffc9db70)        = -1 ENOENT (No such file or 
directory)
open("/lib64/octeon/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or 
directory)
stat("/lib64/octeon", 0xffffc9db70)     = -1 ENOENT (No such file or 
directory)
open("/lib64/libc.so.6", O_RDONLY)      = 3
read(3, 
"\177ELF\2\2\1\0\0\0\0\0\0\0\0\0\0\3\0\10\0\0\0\1\0\0\0\0\0\3Wx"..., 
832) = 832
lseek(3, 59248, SEEK_SET)               = 59248
read(3, 
"\0\0\0\4\0\0\0\20\0\0\0\1GNU\0\0\0\0\0\0\0\0\2\0\0\0\6\0\0\0\n", 32) = 32
fstat(3, {st_mode=S_IFREG|0555, st_size=1680968, ...}) = 0
mmap(NULL, 1604224, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 
0) = 0x5558e43000
mprotect(0x5558fa7000, 61440, PROT_NONE) = 0
mmap(0x5558fb6000, 69632, PROT_READ|PROT_WRITE, 
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x163000) = 0x5558fb6000
mmap(0x5558fc7000, 14976, PROT_READ|PROT_WRITE, 
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x5558fc7000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) 
= 0x5558e32000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) 
= 0x5558e33000
set_thread_area(0x5558e39b00)           = 0
mprotect(0x5558fb6000, 53248, PROT_READ) = 0
mprotect(0x5558e40000, 4096, PROT_READ) = 0
stat("foo.c", {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
fchownat(AT_FDCWD, "foo.c", 4294967295, 0, 0) = 0
fchownat(AT_FDCWD, "foo.c", 55, 4294967295, 0) = 0
fchownat(AT_FDCWD, "foo.c", 4294967295, 4294967295, 0) = 0
exit_group(0)                           = ?