* [PATCH] exfat: fix shift-out-of-bounds in exfat_fill_super()
[not found] <CGME20210129072117epcas1p29cfb23f0ff88f659b404b1d54fb44ee8@epcas1p2.samsung.com>
@ 2021-01-29 7:12 ` Namjae Jeon
2021-01-29 21:10 ` Randy Dunlap
0 siblings, 1 reply; 2+ messages in thread
From: Namjae Jeon @ 2021-01-29 7:12 UTC (permalink / raw)
To: linux-fsdevel; +Cc: willy, rdunlap, sj1557.seo, Namjae Jeon, stable
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 16 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>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
---
fs/exfat/exfat_raw.h | 4 ++++
fs/exfat/super.c | 31 ++++++++++++++++++++++++++-----
2 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h
index 6aec6288e1f2..7c4c356efa5f 100644
--- a/fs/exfat/exfat_raw.h
+++ b/fs/exfat/exfat_raw.h
@@ -77,6 +77,10 @@
#define EXFAT_FILE_NAME_LEN 15
+#define EXFAT_MIN_SECT_SIZE_BITS 9
+#define EXFAT_MAX_SECT_SIZE_BITS 12
+#define EXFAT_MAX_SECT_PER_CLUS_BITS 16
+
/* EXFAT: Main and Backup Boot Sector (512 bytes) */
struct boot_sector {
__u8 jmp_boot[BOOTSEC_JUMP_BOOT_LEN];
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index 87be5bfc31eb..ac5a8f7d2397 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -381,8 +381,7 @@ static int exfat_calibrate_blocksize(struct super_block *sb, int logical_sect)
{
struct exfat_sb_info *sbi = EXFAT_SB(sb);
- if (!is_power_of_2(logical_sect) ||
- logical_sect < 512 || logical_sect > 4096) {
+ if (!is_power_of_2(logical_sect)) {
exfat_err(sb, "bogus logical sector size %u", logical_sect);
return -EIO;
}
@@ -451,6 +450,25 @@ static int exfat_read_boot_sector(struct super_block *sb)
return -EINVAL;
}
+ /*
+ * sect_size_bits could be at least 9 and at most 12.
+ */
+ if (p_boot->sect_size_bits < EXFAT_MIN_SECT_SIZE_BITS ||
+ p_boot->sect_size_bits > EXFAT_MAX_SECT_SIZE_BITS) {
+ exfat_err(sb, "bogus sector size bits : %u\n",
+ p_boot->sect_size_bits);
+ return -EINVAL;
+ }
+
+ /*
+ * sect_per_clus_bits could be at least 0 and at most 16.
+ */
+ if (p_boot->sect_per_clus_bits > EXFAT_MAX_SECT_PER_CLUS_BITS) {
+ exfat_err(sb, "bogus sectors bits per cluster : %u\n",
+ p_boot->sect_per_clus_bits);
+ return -EINVAL;
+ }
+
sbi->sect_per_clus = 1 << p_boot->sect_per_clus_bits;
sbi->sect_per_clus_bits = p_boot->sect_per_clus_bits;
sbi->cluster_size_bits = p_boot->sect_per_clus_bits +
@@ -477,16 +495,19 @@ static int exfat_read_boot_sector(struct super_block *sb)
sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;
/* check consistencies */
- if (sbi->num_FAT_sectors << p_boot->sect_size_bits <
- sbi->num_clusters * 4) {
+ if ((u64)sbi->num_FAT_sectors << p_boot->sect_size_bits <
+ (u64)sbi->num_clusters * 4) {
exfat_err(sb, "bogus fat length");
return -EINVAL;
}
+
if (sbi->data_start_sector <
- sbi->FAT1_start_sector + sbi->num_FAT_sectors * p_boot->num_fats) {
+ (u64)sbi->FAT1_start_sector +
+ (u64)sbi->num_FAT_sectors * p_boot->num_fats) {
exfat_err(sb, "bogus data start sector");
return -EINVAL;
}
+
if (sbi->vol_flags & VOLUME_DIRTY)
exfat_warn(sb, "Volume was not properly unmounted. Some data may be corrupt. Please run fsck.");
if (sbi->vol_flags & MEDIA_FAILURE)
--
2.17.1
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