Re: uid/gid issues on 2.6.26-rc2

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On Sun, 18 May 2008, Thibaut VARENE wrote:

> Then, checking auth.log, I spotted a few very surprising things:
> 
> May 18 09:15:04 mkhppa3 sshd[1265]: Invalid user varenet from 147.215.7.200
> May 18 09:15:04 mkhppa3 sshd[1265]: Failed none for invalid user
> varenet from 147.215.7.200 port 58220 ssh2

I have seen this today testing 2.6.28 (32-bit UP).  The problem is also
present in postfix:

dave@hiauly6:/var/log$ less mail.err
Dec 27 12:45:41 hiauly6 postfix/sendmail[16726]: fatal: file /etc/postfix/main.cf: parameter mail_owner: unknown user name value: postfix

The only place this can occur is here:

static void check_mail_owner(void)
{
    struct passwd *pwd;

    if ((pwd = getpwnam(var_mail_owner)) == 0)
	msg_fatal("file %s/%s: parameter %s: unknown user name value: %s",
		  var_config_dir, MAIN_CONF_FILE,
		  VAR_MAIL_OWNER, var_mail_owner);

So, the problem is with getpwnam.  I don't see this with 2.6.22.19, so
the problem is likely a syscall issue.  These seem to be the syscalls
that directly relate to the getpwnam call:

open("/lib/libnss_files.so.2", O_RDONLY) = 3
read(3, "\177ELF\1\2\1\3\0\0\0\0\0\0\0\0\0\3\0\17\0\0\0\1\0\0$\f\0\0\0004\0"..., 512) = 512
fstat64(3, {st_mode=0, st_size=0, ...}) = 0
mmap(NULL, 52324, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40b92000
mmap(0x40b9e000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xb000) = 0x40b9e000
close(3)                                = 0
munmap(0x4051b000, 30889)               = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40006000
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
fcntl64(3, F_GETFD)                     = 0x1 (flags FD_CLOEXEC)
_llseek(3, 0, [0], SEEK_CUR)            = 0
fstat64(3, {st_mode=0, st_size=0, ...}) = 0
mmap2(NULL, 1557, PROT_READ, MAP_SHARED, 3, 0) = 0x407ae000
_llseek(3, 1557, [1557], SEEK_SET)      = 0
munmap(0x407ae000, 1557)                = 0
close(3)                                = 0
exit_group(0)                           = ?

The failure appears random.  I think the problem occurs shortly after
forking.  It doesn't seem to be present in the 64-bit SMP 2.6.28 test
kernel that I'm testing.

Dave
-- 
J. David Anglin                                  dave.anglin@xxxxxxxxxxxxxx
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)

Attachment: config-uly6.gz
Description: application/gunzip


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