[PATCH v2 1/7] xen: use correct end address of kernel for conflict checking

Juergen Gross posted 7 patches 3 months ago
There is a newer version of this series
[PATCH v2 1/7] xen: use correct end address of kernel for conflict checking
Posted by Juergen Gross 3 months ago
When running as a Xen PV dom0 the kernel is loaded by the hypervisor
using a different memory map than that of the host. In order to
minimize the required changes in the kernel, the kernel adapts its
memory map to that of the host. In order to do that it is checking
for conflicts of its load address with the host memory map.

Unfortunately the tested memory range does not include the .brk
area, which might result in crashes or memory corruption when this
area does conflict withe the memory map of the host.

Fix the test by using the _end label instead of __bss_stop.

Fixes: 808fdb71936c ("xen: check for kernel memory conflicting with memory layout")

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 arch/x86/xen/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 806ddb2391d9..4bcc70a71b7d 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -825,7 +825,7 @@ char * __init xen_memory_setup(void)
 	 * to relocating (and even reusing) pages with kernel text or data.
 	 */
 	if (xen_is_e820_reserved(__pa_symbol(_text),
-			__pa_symbol(__bss_stop) - __pa_symbol(_text))) {
+				 __pa_symbol(_end) - __pa_symbol(_text))) {
 		xen_raw_console_write("Xen hypervisor allocated kernel memory conflicts with E820 map\n");
 		BUG();
 	}
-- 
2.43.0


Re: [PATCH v2 1/7] xen: use correct end address of kernel for conflict checking
Posted by Jan Beulich 3 months ago
On 20.08.2024 10:20, Juergen Gross wrote:
> When running as a Xen PV dom0 the kernel is loaded by the hypervisor
> using a different memory map than that of the host. In order to
> minimize the required changes in the kernel, the kernel adapts its
> memory map to that of the host. In order to do that it is checking
> for conflicts of its load address with the host memory map.
> 
> Unfortunately the tested memory range does not include the .brk
> area, which might result in crashes or memory corruption when this
> area does conflict withe the memory map of the host.
> 
> Fix the test by using the _end label instead of __bss_stop.
> 
> Fixes: 808fdb71936c ("xen: check for kernel memory conflicting with memory layout")
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>