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| author | Tadeusz Struk <tadeusz.struk@linaro.org> | 2022-05-17 08:13:08 +0900 |
|---|---|---|
| committer | Namjae Jeon <linkinjeon@kernel.org> | 2022-05-23 11:17:30 +0900 |
| commit | 64ba4b15e5c045f8b746c6da5fc9be9a6b00b61d (patch) | |
| tree | b53623781c1ada35c64ad9e3d3dad7d66be1b1bb /fs/exfat | |
| parent | 1b6138385499507147e8f654840f4c39afe6adbf (diff) | |
| download | lwn-64ba4b15e5c045f8b746c6da5fc9be9a6b00b61d.tar.gz lwn-64ba4b15e5c045f8b746c6da5fc9be9a6b00b61d.zip | |
exfat: check if cluster num is valid
Syzbot reported slab-out-of-bounds read in exfat_clear_bitmap.
This was triggered by reproducer calling truncute 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
Move the is_valid_cluster() helper from fatent.c to a common
header to make it reusable in other *.c files. And add is_valid_cluster()
to validate if cluster number is within valid range in exfat_clear_bitmap()
and exfat_set_bitmap().
Link: https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
Reported-by: syzbot+a4087e40b9c13aad7892@syzkaller.appspotmail.com
Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Diffstat (limited to 'fs/exfat')
| -rw-r--r-- | fs/exfat/balloc.c | 8 | ||||
| -rw-r--r-- | fs/exfat/exfat_fs.h | 6 | ||||
| -rw-r--r-- | fs/exfat/fatent.c | 6 |
3 files changed, 12 insertions, 8 deletions
diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c index 03f142307174..9f42f25fab92 100644 --- a/fs/exfat/balloc.c +++ b/fs/exfat/balloc.c @@ -148,7 +148,9 @@ int exfat_set_bitmap(struct inode *inode, unsigned int clu, bool sync) struct super_block *sb = inode->i_sb; struct exfat_sb_info *sbi = EXFAT_SB(sb); - WARN_ON(clu < EXFAT_FIRST_CLUSTER); + if (!is_valid_cluster(sbi, clu)) + 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); @@ -166,7 +168,9 @@ void exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync) struct exfat_sb_info *sbi = EXFAT_SB(sb); struct exfat_mount_options *opts = &sbi->options; - WARN_ON(clu < EXFAT_FIRST_CLUSTER); + if (!is_valid_cluster(sbi, clu)) + 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); diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index 82e507413291..4a7a2308eb72 100644 --- a/fs/exfat/exfat_fs.h +++ b/fs/exfat/exfat_fs.h @@ -382,6 +382,12 @@ static inline int exfat_sector_to_cluster(struct exfat_sb_info *sbi, EXFAT_RESERVED_CLUSTERS; } +static inline bool is_valid_cluster(struct exfat_sb_info *sbi, + unsigned int clus) +{ + return clus >= EXFAT_FIRST_CLUSTER && clus < sbi->num_clusters; +} + /* super.c */ int exfat_set_volume_dirty(struct super_block *sb); int exfat_clear_volume_dirty(struct super_block *sb); diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c index 04e1126ce971..9de6a6b844c9 100644 --- a/fs/exfat/fatent.c +++ b/fs/exfat/fatent.c @@ -82,12 +82,6 @@ int exfat_ent_set(struct super_block *sb, unsigned int loc, return 0; } -static inline bool is_valid_cluster(struct exfat_sb_info *sbi, - unsigned int clus) -{ - return clus >= EXFAT_FIRST_CLUSTER && clus < sbi->num_clusters; -} - int exfat_ent_get(struct super_block *sb, unsigned int loc, unsigned int *content) { |