概要

In the Linux kernel, the following vulnerability has been resolved:apparmor: avoid crash when parsed profile name is emptyWhen processing a packed profile in unpack_profile() described like profile :ns::samba-dcerpcd /usr/lib*/samba/{,samba/}samba-dcerpcd {...} a string :samba-dcerpcd is unpacked as a fully-qualified name and thenpassed 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. Lateraa_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 NOPTIKASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]CPU: 6 PID: 1657 Comm: apparmor_parser Not tainted 6.7.0-rc2-dirty #16Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014RIP: 0010:strlen+0x1e/0xa0Call Trace: <TASK&gt; ? 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 </TASK&gt;---[ end trace 0000000000000000 ]---RIP: 0010:strlen+0x1e/0xa0It seems such behaviour of aa_splitn_fqname() is expected and checked inother places where it is called (e.g. aa_remove_profiles). Well, thereis an explicit comment a ns name without a following profile is allowed inside.AFAICS, nothing can prevent unpacked name to be in form like :samba-dcerpcd - it is passed from userspace.Deny the whole profile set replacement in such case and inform user withEPROTO and an explaining message.Found by Linux Verification Center (linuxtesting.org).

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