Bug 2091553 - glibc: Incorrect results of POWER9-optimized strncpy [rhel-8.7.0]
Summary: glibc: Incorrect results of POWER9-optimized strncpy [rhel-8.7.0]
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: glibc
Version: 8.7
Hardware: ppc64le
OS: All
unspecified
medium
Target Milestone: rc
: ---
Assignee: DJ Delorie
QA Contact: Martin Coufal
mtimar
URL:
Whiteboard:
Depends On: 2091549
Blocks: 2094540
TreeView+ depends on / blocked
 
Reported: 2022-05-30 10:05 UTC by Florian Weimer
Modified: 2022-11-11 13:16 UTC (History)
13 users (show)

Fixed In Version: glibc-2.28-205.el8
Doc Type: Bug Fix
Doc Text:
.POWER9-optimized strncpy function no longer gives incorrect results Previously, the POWER9 strncpy function did not use the correct register as the source of the NUL bytes for padding. Consequently, the output buffer contained uninitialized register content instead of the NUL padding. With this update, the strncpy function has been fixed, and the end of the output buffer is now correctly padded with NUL bytes.
Clone Of: 2091549
: 2094540 (view as bug list)
Environment:
Last Closed: 2022-11-08 10:43:12 UTC
Type: Bug
Target Upstream Version:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Bugzilla 1918719 1 None None None 2023-03-03 10:49:26 UTC
Red Hat Issue Tracker RHELPLAN-123641 0 None None None 2022-05-30 10:18:57 UTC
Red Hat Product Errata RHBA-2022:7684 0 None None None 2022-11-08 10:43:40 UTC
Sourceware 29197 0 P2 UNCONFIRMED __strncpy_power9() uses uninitialised register vs18 value for filling after \0 2022-05-30 10:08:27 UTC

Description Florian Weimer 2022-05-30 10:05:33 UTC 
+++ This bug was initially created as a clone of Bug #2091549 +++

Zdenek Sojka reported that strncpy does not always clear the destination buffer. The upstream bug gives the following reproducer:

#include <string.h>
#include <stdlib.h>

#define N 3
char a[N];
char c[N];

int
main (void)
{
  __asm__ volatile ("xxspltib 18, 0xf":::"vs18");
  strncpy (c, a, N);
  for (unsigned i = 0; i < N; i++)
    if (c[i])
      abort ();
  return 0;
}
Comment 8 Matheus Castanho 2022-06-08 14:36:21 UTC 
The fix has been applied upstream for glibc 2.36 and has been backported to all affected versions (glibc >= 2.33).

Commit for glibc 2.36:
https://sourceware.org/git/?p=glibc.git;a=commit;h=0218463dd8265ed937622f88ac68c7d984fe0cfc

Commit for glibc 2.33:
https://sourceware.org/git/?p=glibc.git;a=commit;h=82c7441f04e3c2a653ee29672731e040a1799c6b
Comment 14 errata-xmlrpc 2022-11-08 10:43:12 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (glibc bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2022:7684
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