boot: handle empty initrd files (#40040)

Commit f8fa4222c9ac3e74e91c64e25e9532c99559cf99 added extra logic to
account for the size of the initrds before allocating the required memory pages,
but missed checking if the initrds were empty before allocating memory.

Extend the initrd options only when the initrd is valid, and add extra
check for validating that there is at least one valid initrd file before
allocating memory, fixing the following crash when booting with empty
initrd files:

src/boot/log.c:30@efi_assert: systemd-boot: Assertion
 'BS->AllocatePages(type, memory_type, n_pages, &addr) == EFI_SUCCESS'
failed at /usr/src/debug/systemd-boot/257.8/src/boot/util.h:95@xmalloc_pages, halting.

Fixes: f8fa4222c9ac3e74e91c64e25e9532c99559cf99
("boot: Make initrd_prepare() semantically equivalent to combine_initrds()")

diff --git a/src/boot/boot.c b/src/boot/boot.c
index aa38ff18ee260fa1eb4a3235eb4152c5de44db0a..772edc95a415d7dcefa4fbb386bc68499e460c85 100644 (file)
--- a/src/boot/boot.c
+++ b/src/boot/boot.c
@@ -2443,12 +2443,6 @@ static EFI_STATUS initrd_prepare(
         size_t size = 0, padded_size = 0;
 
         STRV_FOREACH(i, entry->initrd) {
-                _cleanup_free_ char16_t *o = options;
-                if (o)
-                        options = xasprintf("%ls initrd=%ls", o, *i);
-                else
-                        options = xasprintf("initrd=%ls", *i);
-
                 _cleanup_file_close_ EFI_FILE *handle = NULL;
                 err = root->Open(root, &handle, *i, EFI_FILE_MODE_READ, 0);
                 if (err != EFI_SUCCESS)
@@ -2459,6 +2453,15 @@ static EFI_STATUS initrd_prepare(
                 if (err != EFI_SUCCESS)
                         return err;
 
+                if (info->FileSize == 0) /* Automatically skip over empty files */
+                        continue;
+
+                _cleanup_free_ char16_t *o = options;
+                if (o)
+                        options = xasprintf("%ls initrd=%ls", o, *i);
+                else
+                        options = xasprintf("initrd=%ls", *i);
+
                 size_t inc = info->FileSize;
 
                 if (!INC_SAFE(&padded_size, ALIGN4(inc)))
@@ -2466,6 +2469,14 @@ static EFI_STATUS initrd_prepare(
                 assert_se(INC_SAFE(&size, *(i + 1) ? ALIGN4(inc) : inc));
         }
 
+        /* Skip if no valid initrd files */
+        if (padded_size == 0) {
+                *ret_options = NULL;
+                *ret_initrd_pages = (Pages) {};
+                *ret_initrd_size = 0;
+                return EFI_SUCCESS;
+        }
+
         _cleanup_pages_ Pages pages = xmalloc_initrd_pages(padded_size);
         uint8_t *p = PHYSICAL_ADDRESS_TO_POINTER(pages.addr);