D34699.diff
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	diff --git a/usr.sbin/fstyp/msdosfs.c b/usr.sbin/fstyp/msdosfs.c
	--- a/usr.sbin/fstyp/msdosfs.c
	+++ b/usr.sbin/fstyp/msdosfs.c
	@@ -41,6 +41,24 @@

	#define LABEL_NO_NAME "NO NAME "

	+/*
	+ * XXX the signature 0x55 0xAA as the last two bytes of 512 is not required
	+ * by specifications, but was historically required by fstyp. This check
	+ * should be removed, with a more comprehensive BPB validation instead.
	+ */
	+static bool
	+check_signature(uint8_t sector0[512])
	+{
	+ /* Check for the FAT boot sector signature. */
	+ if (sector0[510] == 0x55 && sector0[511] == 0xaa)
	+ return (true);
	+ /* Special case for Raspberry Pi Nano bootloader. */
	+ if (sector0[510] == 0 && sector0[511] == 0 &&
	+ sector0[0] == 0xeb && sector0[1] == 0x3c && sector0[2] == 0x90)
	+ return (true);
	+ return (false);
	+}
	+
	int
	fstyp_msdosfs(FILE fp, char label, size_t size)
	{
	@@ -58,8 +76,7 @@
	if (sector0 == NULL)
	return (1);

	- /* Check for the FAT boot sector signature. */
	- if (sector0[510] != 0x55 \|\| sector0[511] != 0xaa) {
	+ if (!check_signature(sector0)) {
	goto error;
	}