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
Add checks to validate if cluster number is within valid range in
exfat_clear_bitmap() and exfat_set_bitmap()
Cc: Namjae Jeon <[email protected]>
Cc: Sungjong Seo <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
Reported-by: [email protected]
Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
Signed-off-by: Tadeusz Struk <[email protected]>
---
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
2022-04-19 2:39 GMT+09:00, Tadeusz Struk <[email protected]>:
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 <[email protected]>
> Cc: Sungjong Seo <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
>
> Link:
> https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
> Reported-by: [email protected]
> Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
> Signed-off-by: Tadeusz Struk <[email protected]>
> ---
> 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
>
>
2022-04-22 14:54 GMT+09:00, Namjae Jeon <[email protected]>:
> 2022-04-19 2:39 GMT+09:00, Tadeusz Struk <[email protected]>:
> 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 <[email protected]>
>> Cc: Sungjong Seo <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Cc: [email protected]
>>
>> Link:
>> https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
>> Reported-by: [email protected]
>> Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
>> Signed-off-by: Tadeusz Struk <[email protected]>
>> ---
>> 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
>>
>>
>
On 4/29/22 20:26, Namjae Jeon wrote:
>> 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.
Ok, I will try a new version with is_valid_cluster()
--
Thanks,
Tadeusz
Hi Jeon,
On 4/21/22 22:54, Namjae Jeon wrote:
>> 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 ?
Sorry, I missed this.
The reproducer [1] can be found on the syzbot report website [2]
[1] https://syzkaller.appspot.com/text?tag=ReproC&x=1353dfdf700000
[2] https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
--
Thanks,
Tadeusz