Summary

• A vulnerability in the Extended File System (XFS) component of the Linux Kernel could allow a local attacker to cause a denial of service (DoS) condition on a targeted system.
  
  The vulnerability exists in the xfs_bmap_extents_to_btree() function, as defined in the source code file fs/xfs/libxfs/xfs_inode_buf.c, because the affected software performs improper memory operations when mounting XFS filesystems. An attacker could exploit the vulnerability by accessing the system and mounting an XFS filesystem that submits malicious input to the affected software. A successful exploit could cause a NULL pointer dereference memory error and cause the affected software to terminate abnormally, leading to a DoS condition.
  
  Kernel.org has confirmed the vulnerability; however, updates for a stable kernel branch are not available.

Analysis

• To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.

Safeguards

• Administrators are advised to contact the vendor regarding future updates and releases.
  
  Administrators are advised to allow only trusted users to access local systems.
  
  Administrators are advised to allow only privileged users to access administration or management systems.
  
  Administrators are advised to monitor critical systems.

Vendor Announcements

• Kernel.org has confirmed the vulnerability in a bug report at the following link:
  NULL pointer dereference in xfs_bmap_extents_to_btree() when mounting and operating a crafted image

Fixed Software

• Kernel.org has updated the Linux Kernel v4.18-rc4 source code via a git commit at the following link: xfs: More robust inode extent count validation. However, updates to a stable kernel branch were not available at the time that this alert was first published.

Revision History

• Version	Description	Section	Date
  1	Initial public release.	—	2018-July-12

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Affected Products

• The security vulnerability applies to the following combinations of products.
  
  

  Primary Products
  Linus Torvalds	Linux Kernel	2.4.3 (Base) | 2.4.11 (Base) | 2.4.16 (Base) | 2.4.20 (Base) | 2.6.9 (.0) | 2.6.10 (.0) | 2.6.16 (.0, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .16, .17, .18, .19, .20, .21, .22, .23, .24, .25, .26, .27, .28, .29, .30, .31, .32, .33, .34, .35, .36, .37, .38, .39, .40, .41, .42, .43, .44, .45, .46, .47, .48, .49, .50, .51, .52, .53, .54, .55, .56, .57, .58, .59, .60, .61, .62) | 2.6.18 (.0, .1, .2, .3, .4, .5, .6, .7, .8) | 2.6.27 (.0, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .16, .17, .18, .19, .20, .21, .22, .23, .24, .25, .26, .27, .28, .29, .30, .31, .32, .33, .34, .35, .36, .37, .38, .39, .40, .41, .42, .43, .44, .45, .46, .47, .48, .49, .50, .51, .52, .53, .54, .55, .56, .57, .58, .59, .60) | 2.6.28 (.0, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10) | 2.6.29 (.0, .1, .2, .3) | 2.6.32 (Base, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .16, .17, .18, .19, .20, .21, .22, .23, .24, .25, .26, .27, .28, .29, .30, .31, .32, .33, .34, .35, .36, .37, .38, .39, .40, .41, .42, .43, .44, .45, .46, .47, .48, .49, .50, .51, .52, .53, .54, .55, .56, .57, .58, .59, .60, .61, .63) | 2.6.35 (Base, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14) | 2.6.36 (Base, .1, .2, .3, .4) | 2.6.37 (Base, .1, .2, .3, .4, .5, .6) | 2.6.39 (Base, .1, .2, .3, .4) | 3.0 (Base, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .16, .17, .18, .19, .20, .21, .22, .23, .24, .25, .26, .27, .28, .29, .30, .31, .32, .33, .34, .35, .36, .37, .38, .39, .40, .41, .42, .43, .44, .45, .46, .47, .48, .49, .50, .51, .52, .53, .54, .55, .56, .57, .58, .59, .60, .61, .62, .63, .64, .65, .66, .67, .68, .69, .70, .71, .72, .73, .74, .75, .76, .77, .78, .79, .80, .81, .82, .83, .84, .85, .86, .87, .88, .89, .90, .91, .92, .93, .94, .95, .96) | 3.1 (.10) | 3.10 (.1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, 14, .15, .16, .17, .18, .19, .20, .21, .22, .23, .24, .25, .26, .27, .28, .29, .30, .31, .32, .33, .34, .35, .36, .37, .38, .0) | 3.11 (.10) | 3.12 (.19) | 3.14 (.4) | 4.0 (.1, .2, .3, .4, .5, .6) | 4.1 (Base, .1, .2, .3, .4, .5) | 4.2 (Base, .0, .1, .2, .3, .4, .5, .6) | 4.3 (Base, .3, .1, .6) | 4.4 (.0, .2, .1, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .16, .17, .18, .19, .20, .21, .22, .23, .24, .25, .26, .105, .111) | 4.6 (.0, .1, .2, -rc1, .3) | 4.5 (Base, .1, .2, .3, .4) | 4.7 (Base, .1, .2, .3, .4, .5, .6, .7, .8, .9) | 4.8 (Base, .1, .2, .3, .12, .11, .10, .9, .8, .7, .6, .5, .4) | 4.9 (Base) | 4.9.11 (Base) | 4.9.10 (Base) | 4.9.9 (Base) | 4.9.8 (Base) | 4.9.7 (Base) | 4.9.6 (Base) | 4.9.5 (Base) | 4.9.4 (Base) | 4.9.3 (Base) | 4.9.2 (Base) | 4.9.1 (Base) | 4.10 (.0, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .15) | 4.11 (Base, .1, .2, .3, .4, .5, .6, .7) | 4.12 (Base, .1, .2, .3, .4, .5, .6, .7, .8, .9) | 4.13 (.0, .2, .6) | 4.14 (.0, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .0-rc1) | 4.15 (Base, .1, .2, .3, .0, .0-r7, .6, .7, .5, .4, .0-rc4, .8, .9, .10, .11, .13, .14, .15) | 4.16 (Base, .1, .2, .3, .4, .5, .6, .7, .8, .9, .10, .11, .12, .13, .14, .15, .16, .17) | 4.9.76 (Base) | 4.17 (Base, .1, .2)

  Associated Products