[xen master] device-tree/kernel: Use memcpy in output_length()

[patchbot@xxxxxxx]

commit 384a399d21589cfe2b9286d2e356ad784b713cfe
Author:     Michal Orzel <michal.orzel@xxxxxxx>
AuthorDate: Tue Jul 22 09:46:45 2025 +0200
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
CommitDate: Wed Jul 23 12:39:50 2025 -0700

    device-tree/kernel: Use memcpy in output_length()
    
    Trying to boot a compressed kernel with UBSAN enabled, results in the
    following warning:
    (XEN) UBSAN: Undefined behaviour in common/device-tree/kernel.c:21:12
    (XEN) load of misaligned address 00000a0040f89867 for type 'uint32_t'
    (XEN) which requires 4 byte alignment
    ...
    (XEN)    [<00000a0000529964>] kernel_decompress+0x2bc/0x5bc
    (XEN)    [<00000a000052a354>] kernel_probe+0x6f0/0x734
    (XEN)    [<00000a0000528714>] dom0less-build.c#construct_domU+0x188/0x9d8
    
    If &image[image_len - 4] is not aligned to 4B boundary it causes
    unaligned access which is undefined behavior on Arm. Use memcpy instead
    to be safe.
    
    Fixes: c1be0b102e0e ("xen/arm: support gzip compressed kernels")
    Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
    Acked-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
---
 xen/common/device-tree/kernel.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/common/device-tree/kernel.c b/xen/common/device-tree/kernel.c
index ef393182b6..28096121a5 100644
--- a/xen/common/device-tree/kernel.c
+++ b/xen/common/device-tree/kernel.c
@@ -18,7 +18,11 @@
 
 static uint32_t __init output_length(char *image, unsigned long image_len)
 {
-    return *(uint32_t *)&image[image_len - 4];
+    uint32_t val;
+
+    memcpy(&val, &image[image_len - 4], sizeof(val));
+
+    return val;
 }
 
 int __init kernel_decompress(struct boot_module *mod, uint32_t offset)
--
generated by git-patchbot for /home/xen/git/xen.git#master