Bug 1775803 (CVE-2019-19039) - CVE-2019-19039 kernel: information disclosure in __btrfs_free_extent in fs/btrfs/extent-tree.c
Summary: CVE-2019-19039 kernel: information disclosure in __btrfs_free_extent in fs/bt...
Alias: CVE-2019-19039
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 1775804
Blocks: 1775805
TreeView+ depends on / blocked
Reported: 2019-11-22 20:42 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 20:59 UTC (History)
47 users (show)

Fixed In Version:
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Last Closed: 2020-01-28 06:09:06 UTC

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Description Guilherme de Almeida Suckevicz 2019-11-22 20:42:44 UTC
__btrfs_free_extent in fs/btrfs/extent-tree.c in the Linux kernel through 5.3.12 calls btrfs_print_leaf in a certain ENOENT case, which allows local users to obtain potentially sensitive information about register values via the dmesg program.


Comment 1 Guilherme de Almeida Suckevicz 2019-11-22 20:43:14 UTC
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1775804]

Comment 2 Wade Mealing 2020-01-28 05:49:17 UTC
Another party  currently has this issue marked as DISPUTED in the NVD database.  

The reason that this is disputed is because the 'register' information is no different than any of the other warnings that show backtracer/register information to system logs.  See the Mitigation heading for information on how to prevent this on a system.

Comment 3 Wade Mealing 2020-01-28 05:54:51 UTC

Its likely that this flaw will not end up being fixed, due to this being expected behavior.

If this behavior is not derirable, it  can be mitigated by explicitly setting the kernel parameter to restrict non privileged users  with the command:

sudo sysctl -w kernel.dmesg_restrict=1

And to make persistent between systme reboots.

echo 'kernel.dmesg_restrict=1' | sudo tee -a /etc/sysctl.conf

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