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Bug
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Resolution: Unresolved
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Minor
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None
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rhel-8.10, rhel-9.4
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None
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None
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Moderate
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rhel-sst-idm-sssd
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ssg_idm
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None
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False
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None
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Red Hat Enterprise Linux
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None
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None
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None
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All
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None
What were you trying to do that didn't work?
When executing the csh shell while already being a AD user, the next user resolution will fail, as shown in the example below:
[root@winbind ~]# su - winuser@win23.local -s /bin/bash [WIN23\winuser@winbind ~]$ csh [WIN23\winuser@winbind ~]$ cd ~winuser@win23.local Unknown user: winuser@win23.local.
The reason for this is csh will initially resolve the username, which leads to starting the NSS library and have file descriptor 3 be "maintained".
Then csh closes all file descriptors, including file descriptor 3, as its startup procedure.
Finally once prompt is displayed and cd ~winuser@win23.local is issued, which causes the winbind NSS library to be called and use file descriptor 3, which is now dead, hence fails with EBADF.
Due to this, next NSS method gets tried (systemd) but this fails as well, causing the "Unknown user" to be returned by csh.
There is a bug in the NSS library, because the file descriptor is dead, poll() on line 711 returns POLLNVAL, which is not handled in the code. If it was a retry would happen and all would be good:
674 static int winbind_write_sock(struct winbindd_context *ctx, void *buffer, 675 int count, int recursing, int need_priv) 676 { : 703 ret = poll(&pfd, 1, -1); 704 if (ret == -1) { 705 winbind_close_sock(ctx); 706 return -1; /* poll error */ 707 } 708 709 /* Write should be OK if fd not available for reading */ 710 711 >>>>> if ((ret == 1) && (pfd.revents & (POLLIN|POLLHUP|POLLERR))) { 712 713 /* Pipe has closed on remote end */ 714 715 winbind_close_sock(ctx); 716 goto restart; 717 } 718 719 /* Do the write */ 720 721 result = write(fd, (char *)buffer + nwritten, 722 count - nwritten); 723 724 if ((result == -1) || (result == 0)) { 725 726 /* Write failed */ 727 728 winbind_close_sock(ctx); 729 return -1; 730 }
Please provide the package NVR for which bug is seen:
samba-winbind-modules-4.19.4-4.el8_10.x86_64
samba-winbind-modules on RHEL9 (untested, but reading the source code, which is similar)
How reproducible:
Always
Steps to reproduce
- Login with bash as a AD user
- Execute csh
- Execute
cd ~username
Expected results
no error message
Actual results
Unknown user: username.
