[xen staging] x86/PVH: account for module command line length

[patchbot@xxxxxxx]

commit 989584e532c9517a0f789e993f5f6744beaebe3e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Mar 27 12:21:08 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 27 12:21:08 2025 +0100

    x86/PVH: account for module command line length
    
    As per observation in practice, initrd->cmdline_pa is not normally zero.
    Hence so far we always appended at least one byte. That alone may
    already render insufficient the "allocation" made by find_memory().
    Things would be worse when there's actually a (perhaps long) command
    line.
    
    Skip setup when the command line is empty. Amend the "allocation" size
    by padding and actual size of module command line. Along these lines
    also skip initrd setup when the initrd is zero size.
    
    Fixes: 0ecb8eb09f9f ("x86/pvh: pass module command line to dom0")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
---
 xen/arch/x86/hvm/dom0_build.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index 13a7385432..daf1b6f88b 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -652,6 +652,7 @@ static int __init pvh_load_kernel(
     unsigned long image_len = image->size;
     unsigned long initrd_len = initrd ? initrd->size : 0;
     const char *cmdline = image->cmdline_pa ? __va(image->cmdline_pa) : NULL;
+    const char *initrd_cmdline = NULL;
     struct elf_binary elf;
     struct elf_dom_parms parms;
     size_t extra_space;
@@ -715,7 +716,23 @@ static int __init pvh_load_kernel(
     extra_space = sizeof(start_info);
 
     if ( initrd )
-        extra_space += sizeof(mod) + ROUNDUP(initrd_len, PAGE_SIZE);
+    {
+        size_t initrd_space = elf_round_up(&elf, initrd_len);
+
+        if ( initrd->cmdline_pa )
+        {
+            initrd_cmdline = __va(initrd->cmdline_pa);
+            if ( !*initrd_cmdline )
+                initrd_cmdline = NULL;
+        }
+        if ( initrd_cmdline )
+            initrd_space += strlen(initrd_cmdline) + 1;
+
+        if ( initrd_space )
+            extra_space += ROUNDUP(initrd_space, PAGE_SIZE) + sizeof(mod);
+        else
+            initrd = NULL;
+    }
 
     if ( cmdline )
         extra_space += elf_round_up(&elf, strlen(cmdline) + 1);
@@ -740,12 +757,11 @@ static int __init pvh_load_kernel(
         mod.paddr = last_addr;
         mod.size = initrd_len;
         last_addr += elf_round_up(&elf, initrd_len);
-        if ( initrd->cmdline_pa )
+        if ( initrd_cmdline )
         {
-            char *str = __va(initrd->cmdline_pa);
-            size_t len = strlen(str) + 1;
+            size_t len = strlen(initrd_cmdline) + 1;
 
-            rc = hvm_copy_to_guest_phys(last_addr, str, len, v);
+            rc = hvm_copy_to_guest_phys(last_addr, initrd_cmdline, len, v);
             if ( rc )
             {
                 printk("Unable to copy module command line\n");
--
generated by git-patchbot for /home/xen/git/xen.git#staging