CVE-2024-49994 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
block: fix integer overflow in BLKSECDISCARD
I independently rediscovered
commit 22d24a544b0d49bbcbd61c8c0eaf77d3c9297155 block: fix overflow in blk_ioctl_discard()
but for secure erase.
Same problem:
uint64_t r[2] = {512, 18446744073709551104ULL};
ioctl(fd, BLKSECDISCARD, r);
will enter near infinite loop inside blkdev_issue_secure_erase():
a.out: attempt to access beyond end of device loop0: rw=5, sector=3399043073, nr_sectors = 1024 limit=2048 bio_check_eod: 3286214 callbacks suppressed
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Analysis
by VulDB Data Team • 03/22/2026
The vulnerability CVE-2024-49994 represents a critical integer overflow issue within the Linux kernel's block layer subsystem specifically affecting the BLKSECDISCARD ioctl command. This flaw resides in the secure erase functionality that handles discard operations on block devices, where the kernel fails to properly validate input parameters leading to potential denial of service conditions. The vulnerability manifests when processing large discard requests that exceed the maximum representable value for 64-bit integers, creating a scenario where the kernel enters an infinite loop during the secure erase process. This issue directly relates to CWE-191 Integer Underflow/Overflow, which is classified under the weakness category of integer manipulation errors that can lead to unpredictable behavior and system instability.
The technical implementation of this vulnerability occurs through the interaction between the user-space application and kernel-space block device handling routines. When a user-space program issues an ioctl call with BLKSECDISCARD and provides specific parameter values such as the uint64_t array containing {512, 18446744073709551104ULL}, the kernel's blkdev_issue_secure_erase() function receives these parameters without proper bounds checking. The problematic calculation results in a scenario where the sector count parameter becomes excessively large, causing the kernel to attempt operations that exceed the device's physical boundaries. This overflow condition triggers a near infinite loop within the block layer's processing, as evidenced by the debug messages showing sector=3399043073 with nr_sectors=1024 limit=2048, where the kernel repeatedly attempts to access beyond the end of the device. The system generates callback suppression messages indicating the severity and persistence of this condition.
The operational impact of CVE-2024-49994 extends beyond simple denial of service to potentially compromise system stability and availability. An attacker with access to a device file or the ability to execute privileged operations could exploit this vulnerability to consume excessive CPU resources and memory through the infinite loop, effectively rendering the system unresponsive. The vulnerability affects any system running a Linux kernel version containing the affected code path, particularly impacting storage subsystems and applications that rely on secure discard operations. This issue aligns with ATT&CK technique T1490, where adversaries may use resource exhaustion attacks to disrupt system availability, and T1566, which involves gaining access to systems through various attack vectors. The vulnerability demonstrates the importance of proper input validation in kernel-space operations and highlights the risks associated with integer overflow conditions in low-level system components.
Mitigation strategies for CVE-2024-49994 require immediate kernel updates from vendors providing security patches addressing the specific integer overflow in the BLKSECDISCARD implementation. System administrators should ensure all production systems are updated with the latest kernel versions that contain the fix for commit 22d24a544b0d49bbcbd61c8c0eaf77d3c9297155. In addition to patch management, monitoring systems should be configured to detect unusual patterns in block device operations and ioctl calls that might indicate exploitation attempts. Organizations should implement proper access controls and privilege separation to limit which users or processes can execute discard operations on block devices. The fix implemented in the kernel addresses the root cause by adding proper bounds checking and overflow detection before proceeding with the secure erase operations, preventing the infinite loop condition that was previously possible through malformed ioctl parameters. Security teams should also consider implementing runtime protections and anomaly detection systems to identify and respond to potential exploitation attempts before they can cause system-wide disruption.