CVE-2023-52443

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> apparmor: avoid crash when parsed profile name is empty<br /> <br /> When processing a packed profile in unpack_profile() described like<br /> <br /> "profile :ns::samba-dcerpcd /usr/lib*/samba/{,samba/}samba-dcerpcd {...}"<br /> <br /> a string ":samba-dcerpcd" is unpacked as a fully-qualified name and then<br /> passed to aa_splitn_fqname().<br /> <br /> aa_splitn_fqname() treats ":samba-dcerpcd" as only containing a namespace.<br /> Thus it returns NULL for tmpname, meanwhile tmpns is non-NULL. Later<br /> aa_alloc_profile() crashes as the new profile name is NULL now.<br /> <br /> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI<br /> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]<br /> CPU: 6 PID: 1657 Comm: apparmor_parser Not tainted 6.7.0-rc2-dirty #16<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014<br /> RIP: 0010:strlen+0x1e/0xa0<br /> Call Trace:<br /> <br /> ? strlen+0x1e/0xa0<br /> aa_policy_init+0x1bb/0x230<br /> aa_alloc_profile+0xb1/0x480<br /> unpack_profile+0x3bc/0x4960<br /> aa_unpack+0x309/0x15e0<br /> aa_replace_profiles+0x213/0x33c0<br /> policy_update+0x261/0x370<br /> profile_replace+0x20e/0x2a0<br /> vfs_write+0x2af/0xe00<br /> ksys_write+0x126/0x250<br /> do_syscall_64+0x46/0xf0<br /> entry_SYSCALL_64_after_hwframe+0x6e/0x76<br /> <br /> ---[ end trace 0000000000000000 ]---<br /> RIP: 0010:strlen+0x1e/0xa0<br /> <br /> It seems such behaviour of aa_splitn_fqname() is expected and checked in<br /> other places where it is called (e.g. aa_remove_profiles). Well, there<br /> is an explicit comment "a ns name without a following profile is allowed"<br /> inside.<br /> <br /> AFAICS, nothing can prevent unpacked "name" to be in form like<br /> ":samba-dcerpcd" - it is passed from userspace.<br /> <br /> Deny the whole profile set replacement in such case and inform user with<br /> EPROTO and an explaining message.<br /> <br /> Found by Linux Verification Center (linuxtesting.org).