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In the Linux kernel, the following vulnerability has been...

High severity Unreviewed Published Feb 27, 2024 to the GitHub Advisory Database • Updated Apr 12, 2024

Package

No package listed— Suggest a package

Affected versions

Unknown

Patched versions

Unknown

Description

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sch_frag: fix stack OOB read while fragmenting IPv4 packets

when 'act_mirred' tries to fragment IPv4 packets that had been previously
re-assembled using 'act_ct', splats like the following can be observed on
kernels built with KASAN:

BUG: KASAN: stack-out-of-bounds in ip_do_fragment+0x1b03/0x1f60
Read of size 1 at addr ffff888147009574 by task ping/947

CPU: 0 PID: 947 Comm: ping Not tainted 5.12.0-rc6+ #418
Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
Call Trace:

dump_stack+0x92/0xc1
print_address_description.constprop.7+0x1a/0x150
kasan_report.cold.13+0x7f/0x111
ip_do_fragment+0x1b03/0x1f60
sch_fragment+0x4bf/0xe40
tcf_mirred_act+0xc3d/0x11a0 [act_mirred]
tcf_action_exec+0x104/0x3e0
fl_classify+0x49a/0x5e0 [cls_flower]
tcf_classify_ingress+0x18a/0x820
__netif_receive_skb_core+0xae7/0x3340
__netif_receive_skb_one_core+0xb6/0x1b0
process_backlog+0x1ef/0x6c0
__napi_poll+0xaa/0x500
net_rx_action+0x702/0xac0
__do_softirq+0x1e4/0x97f
do_softirq+0x71/0x90

__local_bh_enable_ip+0xdb/0xf0
ip_finish_output2+0x760/0x2120
ip_do_fragment+0x15a5/0x1f60
__ip_finish_output+0x4c2/0xea0
ip_output+0x1ca/0x4d0
ip_send_skb+0x37/0xa0
raw_sendmsg+0x1c4b/0x2d00
sock_sendmsg+0xdb/0x110
__sys_sendto+0x1d7/0x2b0
__x64_sys_sendto+0xdd/0x1b0
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f82e13853eb
Code: 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 f3 0f 1e fa 48 8d 05 75 42 2c 00 41 89 ca 8b 00 85 c0 75 14 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 75 c3 0f 1f 40 00 41 57 4d 89 c7 41 56 41 89
RSP: 002b:00007ffe01fad888 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00005571aac13700 RCX: 00007f82e13853eb
RDX: 0000000000002330 RSI: 00005571aac13700 RDI: 0000000000000003
RBP: 0000000000002330 R08: 00005571aac10500 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe01faefb0
R13: 00007ffe01fad890 R14: 00007ffe01fad980 R15: 00005571aac0f0a0

The buggy address belongs to the page:
page:000000001dff2e03 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x147009
flags: 0x17ffffc0001000(reserved)
raw: 0017ffffc0001000 ffffea00051c0248 ffffea00051c0248 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888147009400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888147009480: f1 f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 00 00 00 00

ffff888147009500: 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 f2
^
ffff888147009580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888147009600: 00 00 00 00 00 00 00 00 00 00 00 00 00 f2 f2 f2

for IPv4 packets, sch_fragment() uses a temporary struct dst_entry. Then,
in the following call graph:

ip_do_fragment()
ip_skb_dst_mtu()
ip_dst_mtu_maybe_forward()
ip_mtu_locked()

the pointer to struct dst_entry is used as pointer to struct rtable: this
turns the access to struct members like rt_mtu_locked into an OOB read in
the stack. Fix this changing the temporary variable used for IPv4 packets
in sch_fragment(), similarly to what is done for IPv6 few lines below.

References

Published by the National Vulnerability Database Feb 27, 2024
Published to the GitHub Advisory Database Feb 27, 2024
Last updated Apr 12, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

EPSS score

0.042%
(5th percentile)

Weaknesses

CVE ID

CVE-2021-46954

GHSA ID

GHSA-6jf4-4jp9-4wmw

Source code

No known source code

Dependabot alerts are not supported on this advisory because it does not have a package from a supported ecosystem with an affected and fixed version.

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