From ae9d8058f13238cad5f5d16f676da91187684581 Mon Sep 17 00:00:00 2001 From: Nikolay Ivchenko Date: Sat, 20 Jun 2026 20:06:03 +0300 Subject: [PATCH] mtd: mtdpart: fix uninitialized erasesize on MTDPART_OFS_RETAIN error path When parsing partition layouts, if a partition requested with MTDPART_OFS_RETAIN runs out of space, the allocator jumps directly to 'out_register' to preserve partition numbering. However, this jump bypasses child->erasesize initialization, leaving it at zero. When add_mtd_device() is later called on this child, the registration fails and triggers a WARN_ON() due to the zero ->erasesize. Fix this by zeroing out child->part.offset and child->part.size, and initializing child->erasesize to parent->erasesize. This is the exact same pattern already used just a few lines below in the "out of reach" error check (child->part.offset >= parent_size) to safely register a disabled partition. Reported-by: syzbot+3ae80219c633aca5431c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3ae80219c633aca5431c Signed-off-by: Nikolay Ivchenko Signed-off-by: Miquel Raynal --- drivers/mtd/mtdpart.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c index 795a94e6b482..7f23f8a1b59c 100644 --- a/drivers/mtd/mtdpart.c +++ b/drivers/mtd/mtdpart.c @@ -118,6 +118,9 @@ static struct mtd_info *allocate_partition(struct mtd_info *parent, part->name, parent_size - child->part.offset, child->part.size); /* register to preserve ordering */ + child->part.offset = 0; + child->part.size = 0; + child->erasesize = parent->erasesize; goto out_register; } }