CVE-2012-2100: Divide by Zero
Commit 503358ae01b70ce6909d19dd01287093f6b6271c ("ext4: avoid divide by zero when trying to mount a corrupted file system") fixes CVE-2009-4307 by performing a sanity check on sloggroupsperflex, since it can be set to a bogus value by an attacker.
More info from Wang Xi: The first commit (503358ae) fixes the division by zero. The fix is not perfect because: 1) Theoretically, a standard-conforming C compiler could generate code that is still vulnerable to division by zero, but I was not aware of any compilers doing that. 2) Logically, we should have groupsperflex = 2^sloggroupsperflex, and the fix doesn't really ensure that. This is obviously not good, but not sure how bad the consequence would be.
Introduced by: http://git.kernel.org/linus/503358ae01b70ce6909d19dd01287093f6b6271c
Upstream commit: http://git.kernel.org/linus/d50f2ab6f050311dbf7b8f5501b25f0bf64a439b
Other sources
The ext4fillflexinfo function in fs/ext4/super.c in the Linux kernel before 3.2.2, on the x86 platform and unspecified other platforms, allows user-assisted remote attackers to trigger inconsistent filesystem-groups data and possibly cause a denial of service via a malformed ext4 filesystem containing a super block with a large FLEXBG group size (aka sloggroupsperflex value). NOTE: this vulnerability exists because of an incomplete fix for CVE-2009-4307.
— Debian
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2012-2100?
CVE-2012-2100 is classified as a high-severity vulnerability that could potentially lead to data loss or system instability.
How do I fix CVE-2012-2100?
To fix CVE-2012-2100, update to a Linux kernel version newer than 3.2.1 or apply security patches provided by your distribution.
Which systems are affected by CVE-2012-2100?
CVE-2012-2100 affects Linux kernel versions up to 3.2.1 and specifically includes the Debian linux-2.6 package.
What type of vulnerability is CVE-2012-2100?
CVE-2012-2100 is a vulnerability that relates to a potential divide by zero error when mounting a corrupted ext4 file system.
Is CVE-2012-2100 being actively exploited?
As of now, there have been no reported active exploitations of CVE-2012-2100, but it is critical to patch the vulnerability to prevent potential attacks.