On 1/31/21 6:46 PM, Namjae Jeon wrote:
syzbot reported a warning which could cause shift-out-of-bounds issue.
Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x183/0x22e lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:148 [inline] __ubsan_handle_shift_out_of_bounds+0x432/0x4d0 lib/ubsan.c:395 exfat_read_boot_sector fs/exfat/super.c:471 [inline] __exfat_fill_super fs/exfat/super.c:556 [inline] exfat_fill_super+0x2acb/0x2d00 fs/exfat/super.c:624 get_tree_bdev+0x406/0x630 fs/super.c:1291 vfs_get_tree+0x86/0x270 fs/super.c:1496 do_new_mount fs/namespace.c:2881 [inline] path_mount+0x1937/0x2c50 fs/namespace.c:3211 do_mount fs/namespace.c:3224 [inline] __do_sys_mount fs/namespace.c:3432 [inline] __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3409 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9
exfat specification describe sect_per_clus_bits field of boot sector could be at most 25 - sect_size_bits and at least 0. And sect_size_bits can also affect this calculation, It also needs validation. This patch add validation for sect_per_clus_bits and sect_size_bits field of boot sector.
Fixes: 719c1e182916 ("exfat: add super block operations") Cc: stable@vger.kernel.org # v5.9+ Reported-by: syzbot+da4fe66aaadd3c2e2d1c@syzkaller.appspotmail.com Reviewed-by: Sungjong Seo sj1557.seo@samsung.com Tested-by: Randy Dunlap rdunlap@infradead.org Signed-off-by: Namjae Jeon namjae.jeon@samsung.com
Tested-by: Randy Dunlap rdunlap@infradead.org # for v2
Thanks for your testing!
v2:
- change at most sect_per_clus_bits from 16 to 25 - sect_size_bits.
fs/exfat/exfat_raw.h | 4 ++++ fs/exfat/super.c | 31 ++++++++++++++++++++++++++----- 2 files changed, 30 insertions(+), 5 deletions(-)
thanks.
~Randy