2022-04-19 2:39 GMT+09:00, Tadeusz Struk <tadeusz.struk@xxxxxxxxxx>: Hi Tadeusz, > Syzbot reported slab-out-of-bounds read in exfat_clear_bitmap. > This was triggered by reproducer calling truncate with size 0, > which causes the following trace: > > BUG: KASAN: slab-out-of-bounds in exfat_clear_bitmap+0x147/0x490 > fs/exfat/balloc.c:174 > Read of size 8 at addr ffff888115aa9508 by task syz-executor251/365 > > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack_lvl+0x1e2/0x24b lib/dump_stack.c:118 > print_address_description+0x81/0x3c0 mm/kasan/report.c:233 > __kasan_report mm/kasan/report.c:419 [inline] > kasan_report+0x1a4/0x1f0 mm/kasan/report.c:436 > __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309 > exfat_clear_bitmap+0x147/0x490 fs/exfat/balloc.c:174 > exfat_free_cluster+0x25a/0x4a0 fs/exfat/fatent.c:181 > __exfat_truncate+0x99e/0xe00 fs/exfat/file.c:217 > exfat_truncate+0x11b/0x4f0 fs/exfat/file.c:243 > exfat_setattr+0xa03/0xd40 fs/exfat/file.c:339 > notify_change+0xb76/0xe10 fs/attr.c:336 > do_truncate+0x1ea/0x2d0 fs/open.c:65 Could you please share how to reproduce this ? Thanks. > > Add checks to validate if cluster number is within valid range in > exfat_clear_bitmap() and exfat_set_bitmap() > > Cc: Namjae Jeon <linkinjeon@xxxxxxxxxx> > Cc: Sungjong Seo <sj1557.seo@xxxxxxxxxxx> > Cc: linux-fsdevel@xxxxxxxxxxxxxxx > Cc: stable@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > > Link: > https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c > Reported-by: syzbot+a4087e40b9c13aad7892@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: 1e49a94cf707 ("exfat: add bitmap operations") > Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> > --- > fs/exfat/balloc.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c > index 03f142307174..4ed81f86f993 100644 > --- a/fs/exfat/balloc.c > +++ b/fs/exfat/balloc.c > @@ -149,6 +149,9 @@ int exfat_set_bitmap(struct inode *inode, unsigned int > clu, bool sync) > struct exfat_sb_info *sbi = EXFAT_SB(sb); > > WARN_ON(clu < EXFAT_FIRST_CLUSTER); > + if (clu > EXFAT_DATA_CLUSTER_COUNT(sbi)) > + return -EINVAL; > + > ent_idx = CLUSTER_TO_BITMAP_ENT(clu); > i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx); > b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx); > @@ -167,6 +170,9 @@ void exfat_clear_bitmap(struct inode *inode, unsigned > int clu, bool sync) > struct exfat_mount_options *opts = &sbi->options; > > WARN_ON(clu < EXFAT_FIRST_CLUSTER); > + if (clu > EXFAT_DATA_CLUSTER_COUNT(sbi)) > + return; > + > ent_idx = CLUSTER_TO_BITMAP_ENT(clu); > i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx); > b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx); > -- > 2.35.1 > >
