fastboot: handle small flash block sizes correctly

Erase block sizes smaller than the ext4 block size may be valid, but
can incorrectly result in a stripe width smaller than the stride
size. Instead of reporting these sizes as invalid, add a check to
enforce that raid_stripe_width >= raid_stride.

Bug: 68770797
Test: Hack fb_getvar to report small erase block size, run fastboot
-w and confirm it does not print a warning or set stripe_width smaller
than stride.
Signed-off-by: Connor O'Brien <connoro@google.com>

Change-Id: I689ce4bdd5b38bd0952bb6de54785cca39176010

1 files changed, 2 insertions, 3 deletions

diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index c3b1bfb2e..222d64fd1 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -1365,9 +1365,8 @@ static unsigned fb_get_flash_block_size(Transport* transport, std::string name)
         fprintf(stderr, "Couldn't parse %s '%s'.\n", name.c_str(), sizeString.c_str());
         return 0;
     }
-    if (size < 4096 || (size & (size - 1)) != 0) {
-        fprintf(stderr, "Invalid %s %u: must be a power of 2 and at least 4096.\n",
-                name.c_str(), size);
+    if ((size & (size - 1)) != 0) {
+        fprintf(stderr, "Invalid %s %u: must be a power of 2.\n", name.c_str(), size);
         return 0;
     }
     return size;