CVE-2024-26921
Linux kernel Vulnerability: "inet Fragment Skew"
Description
In the Linux kernel, the following vulnerability has been resolved: inet: inet_defrag: prevent sk release while still in use ip_local_out() and other functions can pass skb->sk as function argument. If the skb is a fragment and reassembly happens before such function call returns, the sk must not be released. This affects skb fragments reassembled via netfilter or similar modules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline. Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing. A relevant old patch about the issue was : 8282f27449bf ("inet: frag: Always orphan skbs inside ip_defrag()") [..] net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one. If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly. We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used. Eric suggested to stash sk in fragment queue and made an initial patch. However there is a problem with this: If skb is refragmented again right after, ip_do_fragment() will copy head->sk to the new fragments, and sets up destructor to sock_wfree. IOW, we have no choice but to fix up sk_wmem accouting to reflect the fully reassembled skb, else wmem will underflow. This change moves the orphan down into the core, to last possible moment. As ip_defrag_offset is aliased with sk_buff->sk member, we must move the offset into the FRAG_CB, else skb->sk gets clobbered. This allows to delay the orphaning long enough to learn if the skb has to be queued or if the skb is completing the reasm queue. In the former case, things work as before, skb is orphaned. This is safe because skb gets queued/stolen and won't continue past reasm engine. In the latter case, we will steal the skb->sk reference, reattach it to the head skb, and fix up wmem accouting when inet_frag inflates truesize.
INFO
Published Date :
April 18, 2024, 10:15 a.m.
Last Modified :
Nov. 21, 2024, 9:03 a.m.
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Remotely Exploitable :
No
Impact Score :
Exploitability Score :
Public PoC/Exploit Available at Github
CVE-2024-26921 has a 1 public PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2024-26921.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
A collection of links related to Linux kernel security and exploitation
linux-kernel kernel-exploitation exploit privilege-escalation security
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2024-26921 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2024-26921 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 21, 2024
Action Type Old Value New Value Added Reference https://git.kernel.org/stable/c/18685451fc4e546fc0e718580d32df3c0e5c8272 Added Reference https://git.kernel.org/stable/c/7d0567842b78390dd9b60f00f1d8f838d540e325 Added Reference https://git.kernel.org/stable/c/e09cbe017311508c21e0739e97198a8388b98981 Added Reference https://git.kernel.org/stable/c/f4877225313d474659ee53150ccc3d553a978727 -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Nov. 08, 2024
Action Type Old Value New Value Added Reference kernel.org https://git.kernel.org/stable/c/1b6de5e6575b56502665c65cf93b0ae6aa0f51ab [No types assigned] -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Oct. 17, 2024
Action Type Old Value New Value Added Reference kernel.org https://git.kernel.org/stable/c/9705f447bf9a6cd088300ad2c407b5e1c6591091 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/4318608dc28ef184158b4045896740716bea23f0 [No types assigned] -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 29, 2024
Action Type Old Value New Value -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 14, 2024
Action Type Old Value New Value -
CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Apr. 18, 2024
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: inet: inet_defrag: prevent sk release while still in use ip_local_out() and other functions can pass skb->sk as function argument. If the skb is a fragment and reassembly happens before such function call returns, the sk must not be released. This affects skb fragments reassembled via netfilter or similar modules, e.g. openvswitch or ct_act.c, when run as part of tx pipeline. Eric Dumazet made an initial analysis of this bug. Quoting Eric: Calling ip_defrag() in output path is also implying skb_orphan(), which is buggy because output path relies on sk not disappearing. A relevant old patch about the issue was : 8282f27449bf ("inet: frag: Always orphan skbs inside ip_defrag()") [..] net/ipv4/ip_output.c depends on skb->sk being set, and probably to an inet socket, not an arbitrary one. If we orphan the packet in ipvlan, then downstream things like FQ packet scheduler will not work properly. We need to change ip_defrag() to only use skb_orphan() when really needed, ie whenever frag_list is going to be used. Eric suggested to stash sk in fragment queue and made an initial patch. However there is a problem with this: If skb is refragmented again right after, ip_do_fragment() will copy head->sk to the new fragments, and sets up destructor to sock_wfree. IOW, we have no choice but to fix up sk_wmem accouting to reflect the fully reassembled skb, else wmem will underflow. This change moves the orphan down into the core, to last possible moment. As ip_defrag_offset is aliased with sk_buff->sk member, we must move the offset into the FRAG_CB, else skb->sk gets clobbered. This allows to delay the orphaning long enough to learn if the skb has to be queued or if the skb is completing the reasm queue. In the former case, things work as before, skb is orphaned. This is safe because skb gets queued/stolen and won't continue past reasm engine. In the latter case, we will steal the skb->sk reference, reattach it to the head skb, and fix up wmem accouting when inet_frag inflates truesize. Added Reference kernel.org https://git.kernel.org/stable/c/7d0567842b78390dd9b60f00f1d8f838d540e325 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/f4877225313d474659ee53150ccc3d553a978727 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/e09cbe017311508c21e0739e97198a8388b98981 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/18685451fc4e546fc0e718580d32df3c0e5c8272 [No types assigned]
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2024-26921 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2024-26921
weaknesses.