• Hector Palacios's avatar
    mtd: nand: fix bug writing 1 byte less than page size · 144f4c98
    Hector Palacios authored
    nand_do_write_ops() determines if it is writing a partial page with the
    formula:
    	part_pagewr = (column || writelen < (mtd->writesize - 1))
    
    When 'writelen' is exactly 1 byte less than the NAND page size the formula
    equates to zero, so the code doesn't process it as a partial write,
    although it should.
    As a consequence the function remains in the while(1) loop with 'writelen'
    becoming 0xffffffff and iterating endlessly.
    
    The bug may not be easy to reproduce in Linux since user space tools
    usually force the padding or round-up the write size to a page-size
    multiple.
    This was discovered in U-Boot where the issue can be reproduced by
    writing any size that is 1 byte less than a page-size multiple.
    For example, on a NAND with 2K page (0x800):
    	=> nand erase.part <partition>
    	=> nand write $loadaddr <partition> 7ff
    
    [Editor's note: the bug was added in commit 29072b96, but moved
    around in commit 66507c7b ("mtd: nand: Add support to use nand_base
    poi databuf as bounce buffer")]
    
    Fixes: 29072b96 ("[MTD] NAND: add subpage write support")
    Signed-off-by: default avatarHector Palacios <hector.palacios@digi.com>
    Acked-by: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
    144f4c98
nand_base.c 120 KB