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mtd: nand: fix bug writing 1 byte less than page size

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commit 144f4c9839 upstream.

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 29072b9607, but moved
around in commit 66507c7bc8 ("mtd: nand: Add support to use nand_base
poi databuf as bounce buffer")]

Fixes: 29072b9607 ("[MTD] NAND: add subpage write support")
Signed-off-by: Hector Palacios <hector.palacios@digi.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hector Palacios 2016-07-18 10:39:18 +02:00 • committed by Greg Kroah-Hartman
commit 7928de5185
1 changed files with 1 additions and 1 deletions
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