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321d628a FG |
1 | From f7b3a0038fd5bdc21d05f09002e16db3ea8e6e3b Mon Sep 17 00:00:00 2001 |
2 | From: Thomas Gleixner <tglx@linutronix.de> | |
3 | Date: Sun, 31 Dec 2017 11:24:34 +0100 | |
633c5ed1 | 4 | Subject: [PATCH 221/242] x86/ldt: Plug memory leak in error path |
321d628a FG |
5 | MIME-Version: 1.0 |
6 | Content-Type: text/plain; charset=UTF-8 | |
7 | Content-Transfer-Encoding: 8bit | |
8 | ||
9 | CVE-2017-5754 | |
10 | ||
11 | The error path in write_ldt() tries to free 'old_ldt' instead of the newly | |
12 | allocated 'new_ldt', resulting in a memory leak. It also misses to clean up a | |
13 | half populated LDT pagetable, which is not a leak as it gets cleaned up | |
14 | when the process exits. | |
15 | ||
16 | Free both the potentially half populated LDT pagetable and the newly | |
17 | allocated LDT struct. This can be done unconditionally because once an LDT | |
18 | is mapped subsequent maps will succeed, because the PTE page is already | |
19 | populated and the two LDTs fit into that single page. | |
20 | ||
21 | Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
22 | Signed-off-by: Thomas Gleixner <tglx@linutronix.de> | |
23 | Cc: Andy Lutomirski <luto@kernel.org> | |
24 | Cc: Borislav Petkov <bp@alien8.de> | |
25 | Cc: Dave Hansen <dave.hansen@linux.intel.com> | |
26 | Cc: Dominik Brodowski <linux@dominikbrodowski.net> | |
27 | Cc: Linus Torvalds <torvalds@linux-foundation.org> | |
28 | Cc: Linus Torvalds <torvalds@linuxfoundation.org> | |
29 | Cc: Peter Zijlstra <peterz@infradead.org> | |
30 | Fixes: f55f0501cbf6 ("x86/pti: Put the LDT in its own PGD if PTI is on") | |
31 | Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1712311121340.1899@nanos | |
32 | Signed-off-by: Ingo Molnar <mingo@kernel.org> | |
33 | (cherry picked from commit a62d69857aab4caa43049e72fe0ed5c4a60518dd) | |
34 | Signed-off-by: Andy Whitcroft <apw@canonical.com> | |
35 | Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> | |
36 | (cherry picked from commit 03d02494f6253d0bdca7254d85e50786448c14f9) | |
37 | Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> | |
38 | --- | |
39 | arch/x86/kernel/ldt.c | 8 +++++++- | |
40 | 1 file changed, 7 insertions(+), 1 deletion(-) | |
41 | ||
42 | diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c | |
43 | index 2260eb6e2de7..9a35b7e541bc 100644 | |
44 | --- a/arch/x86/kernel/ldt.c | |
45 | +++ b/arch/x86/kernel/ldt.c | |
46 | @@ -420,7 +420,13 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) | |
47 | */ | |
48 | error = map_ldt_struct(mm, new_ldt, old_ldt ? !old_ldt->slot : 0); | |
49 | if (error) { | |
50 | - free_ldt_struct(old_ldt); | |
51 | + /* | |
52 | + * This only can fail for the first LDT setup. If an LDT is | |
53 | + * already installed then the PTE page is already | |
54 | + * populated. Mop up a half populated page table. | |
55 | + */ | |
56 | + free_ldt_pgtables(mm); | |
57 | + free_ldt_struct(new_ldt); | |
58 | goto out_unlock; | |
59 | } | |
60 | ||
61 | -- | |
62 | 2.14.2 | |
63 |