linux-kernel - [PATCH 018/145] x86, efi: retry ExitBootServices() on failure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1374101277-7915-19-git-send-email-kamal@canonical.com>
Date:	Wed, 17 Jul 2013 15:45:50 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Zach Bobroff <zacharyb@....com>,
	Matt Fleming <matt.fleming@...el.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 018/145] x86, efi: retry ExitBootServices() on failure

3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zach Bobroff <zacharyb@....com>

commit d3768d885c6ccbf8a137276843177d76c49033a7 upstream.

ExitBootServices is absolutely supposed to return a failure if any
ExitBootServices event handler changes the memory map.  Basically the
get_map loop should run again if ExitBootServices returns an error the
first time.  I would say it would be fair that if ExitBootServices gives
an error the second time then Linux would be fine in returning control
back to BIOS.

The second change is the following line:

again:
        size += sizeof(*mem_map) * 2;

Originally you were incrementing it by the size of one memory map entry.
The issue here is all related to the low_alloc routine you are using.
In this routine you are making allocations to get the memory map itself.
Doing this allocation or allocations can affect the memory map by more
than one record.

[ mfleming - changelog, code style ]
Signed-off-by: Zach Bobroff <zacharyb@....com>
Signed-off-by: Matt Fleming <matt.fleming@...el.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/x86/boot/compressed/eboot.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index c205035..d606463 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -992,18 +992,20 @@ static efi_status_t exit_boot(struct boot_params *boot_params,
 	efi_memory_desc_t *mem_map;
 	efi_status_t status;
 	__u32 desc_version;
+	bool called_exit = false;
 	u8 nr_entries;
 	int i;
 
 	size = sizeof(*mem_map) * 32;
 
 again:
-	size += sizeof(*mem_map);
+	size += sizeof(*mem_map) * 2;
 	_size = size;
 	status = low_alloc(size, 1, (unsigned long *)&mem_map);
 	if (status != EFI_SUCCESS)
 		return status;
 
+get_map:
 	status = efi_call_phys5(sys_table->boottime->get_memory_map, &size,
 				mem_map, &key, &desc_size, &desc_version);
 	if (status == EFI_BUFFER_TOO_SMALL) {
@@ -1029,8 +1031,20 @@ again:
 	/* Might as well exit boot services now */
 	status = efi_call_phys2(sys_table->boottime->exit_boot_services,
 				handle, key);
-	if (status != EFI_SUCCESS)
-		goto free_mem_map;
+	if (status != EFI_SUCCESS) {
+		/*
+		 * ExitBootServices() will fail if any of the event
+		 * handlers change the memory map. In which case, we
+		 * must be prepared to retry, but only once so that
+		 * we're guaranteed to exit on repeated failures instead
+		 * of spinning forever.
+		 */
+		if (called_exit)
+			goto free_mem_map;
+
+		called_exit = true;
+		goto get_map;
+	}
 
 	/* Historic? */
 	boot_params->alt_mem_k = 32 * 1024;
-- 
1.8.1.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/