2022-04-22 14:54 GMT+09:00, Namjae Jeon <linkinjeon@xxxxxxxxxx>: > 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 ? Ping, If you apply this patch to your source, there is a problem. You need to add +1 to EXFAT_DATA_CLUSTER_COUNT(sbi). and please use is_valid_cluster() to check if cluster is valid instead of it. > > 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 >> >> >
