[Bug libc/28770] New: Unexpected return value from realpath() for too long results (CVE-2021-3998)

[Bug libc/28770] New: Unexpected return value from realpath() for too long results (CVE-2021-3998)

[siddhesh at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

            Bug ID: 28770
           Summary: Unexpected return value from realpath() for too long
                    results (CVE-2021-3998)
           Product: glibc
           Version: 2.35
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: siddhesh at sourceware dot org
          Reporter: siddhesh at sourceware dot org
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

When the resolved_path argument for realpath is non-NULL and the result is
longer than PATH_MAX, the return value is an allocated string instead of
resolved_path, which may result in a memory leak since the caller expects
resolved_path.

Another problem with this behaviour is that if the caller uses resolved_path
instead of the return value from realpath; it may potentially end up using
uninitialized memory.

The expected behaviour in case of result being greater than PATH_MAX is to
return NULL and set ENAMETOOLONG.

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[siddhesh at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

Siddhesh Poyarekar <siddhesh at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security+

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[siddhesh at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

Siddhesh Poyarekar <siddhesh at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[aurelien at aurel32 dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

Aurelien Jarno <aurelien at aurel32 dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aurelien at aurel32 dot net

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[pgowda.cve at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

pgowda <pgowda.cve at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pgowda.cve at gmail dot com

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[siddhesh at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

Siddhesh Poyarekar <siddhesh at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.35
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #1 from Siddhesh Poyarekar <siddhesh at sourceware dot org> ---
Fixed on trunk:

commit ee8d5e33adb284601c00c94687bc907e10aec9bb
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Thu Jan 13 11:28:36 2022 +0530

    realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ
#28770]

    realpath returns an allocated string when the result exceeds PATH_MAX,
    which is unexpected when its second argument is not NULL.  This results
    in the second argument (resolved) being uninitialized and also results
    in a memory leak since the caller expects resolved to be the same as the
    returned value.

    Return NULL and set errno to ENAMETOOLONG if the result exceeds
    PATH_MAX.  This fixes [BZ #28770], which is CVE-2021-3998.

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Siddhesh Poyarekar
<siddhesh@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=84d2d0fe20bdf94feed82b21b4d7d136db471f03

commit 84d2d0fe20bdf94feed82b21b4d7d136db471f03
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Mon Jan 24 21:36:41 2022 +0530

    realpath: Avoid overwriting preexisting error (CVE-2021-3998)

    Set errno and failure for paths that are too long only if no other error
    occurred earlier.

    Related: BZ #28770

    Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

--- Comment #3 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The release/2.34/master branch has been updated by Siddhesh Poyarekar
<siddhesh@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d084965adc7baa8ea804427cccf973cea556d697

commit d084965adc7baa8ea804427cccf973cea556d697
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Mon Jan 24 21:36:41 2022 +0530

    realpath: Avoid overwriting preexisting error (CVE-2021-3998)

    Set errno and failure for paths that are too long only if no other error
    occurred earlier.

    Related: BZ #28770

    Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
    (cherry picked from commit 84d2d0fe20bdf94feed82b21b4d7d136db471f03)

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The release/2.34/master branch has been updated by Aurelien Jarno
<aurel32@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1b9cd6a7214db1812a20eb3591cf42f9190a5d1a

commit 1b9cd6a7214db1812a20eb3591cf42f9190a5d1a
Author: Aurelien Jarno <aurelien@aurel32.net>
Date:   Mon Jan 24 23:45:03 2022 +0100

    NEWS: add bug entry for BZ #28769 and BZ #28770

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[Bug libc/28770] Unexpected return value from realpath() for too long results (CVE-2021-3998)

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28770

--- Comment #5 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The release/2.33/master branch has been updated by Aurelien Jarno
<aurel32@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=41980af2d77ecaef34ef5470dc76f6137279e47f

commit 41980af2d77ecaef34ef5470dc76f6137279e47f
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Mon Jan 24 21:36:41 2022 +0530

    realpath: Avoid overwriting preexisting error (CVE-2021-3998)

    Set errno and failure for paths that are too long only if no other error
    occurred earlier.

    Related: BZ #28770

    Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
    Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
    (cherry picked from commit 84d2d0fe20bdf94feed82b21b4d7d136db471f03)

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