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fat: fix fat_ra_init() for data clusters == 0 

If data clusters == 0, fat_ra_init() calls the ->ent_blocknr() for the
cluster beyond ->max_clusters.

This checks the limit before initialization to suppress the warning.

Reported-by: syzbot+756199124937b31a9b7e@syzkaller.appspotmail.com
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/87mu462sv4.fsf@mail.parknet.co.jp
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
OGAWA Hirofumi 2020-08-11 18:36:01 -07:00 committed by Linus Torvalds
parent 4ecfed61de
commit a090a5a7d7
1 changed files with 3 additions and 0 deletions
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3
fs/fat/fatent.c
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@ -657,6 +657,9 @@ static void fat_ra_init(struct super_block *sb, struct fatent_ra *ra,
unsigned long ra_pages = sb->s_bdi->ra_pages;
unsigned int reada_blocks;
if (fatent->entry >= ent_limit)
return;
if (ra_pages > sb->s_bdi->io_pages)
ra_pages = rounddown(ra_pages, sb->s_bdi->io_pages);
reada_blocks = ra_pages << (PAGE_SHIFT - sb->s_blocksize_bits + 1);