CVE-2023-52443 Information

Feb 23, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

apparmor: avoid crash when parsed profile name is empty

When processing a packed profile in unpack_profile() described like

\profile :ns::samba-dcerpcd /usr/lib/samba/samba/samba-dcerpcd …\n a string :samba-dcerpcd\ is unpacked as a fully-qualified name and then passed to aa_splitn_fqname().

aa_splitn_fqname() treats :samba-dcerpcd\ as only containing a namespace. Thus it returns NULL for tmpname meanwhile tmpns is non-NULL. Later aa_alloc_profile() crashes as the new profile name is NULL now.

general protection fault probably for non-canonical address 0xdffffc0000000000: 0000 [1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 6 PID: 1657 Comm: apparmor_parser Not tainted 6.7.0-rc2-dirty 16 Hardware name: QEMU Standard PC (i440FX + PIIX 1996) BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014 RIP: 0010:strlen+0x1e/0xa0 Call Trace: ? strlen+0x1e/0xa0 aa_policy_init+0x1bb/0x230 aa_alloc_profile+0xb1/0x480 unpack_profile+0x3bc/0x4960 aa_unpack+0x309/0x15e0 aa_replace_profiles+0x213/0x33c0 policy_update+0x261/0x370 profile_replace+0x20e/0x2a0 vfs_write+0x2af/0xe00 ksys_write+0x126/0x250 do_syscall_64+0x46/0xf0 entry_SYSCALL_64_after_hwframe+0x6e/0x76 —[ end trace 0000000000000000 ]— RIP: 0010:strlen+0x1e/0xa0

It seems such behaviour of aa_splitn_fqname() is expected and checked in other places where it is called (e.g. aa_remove_profiles). Well there is an explicit comment ns name without a following profile is allowed\ninside.

AFAICS nothing can prevent unpacked ame\ to be in form like :samba-dcerpcd\ - it is passed from userspace.

Deny the whole profile set replacement in such case and inform user with EPROTO and an explaining message.

Found by Linux Verification Center (linuxtesting.org).

Reference

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