[v2] lib/iov_iter: fix to increase non slab folio refcount

[PATCH v2] lib/iov_iter: fix to increase non slab folio refcount

Posted by Sheng Yong 2 days, 20 hours ago

From: Sheng Yong <shengyong1@xiaomi.com>

When testing EROFS file-backed mount over v9fs on qemu, I encountered
a folio UAF issue. The page sanity check reports the following call
trace. The root cause is that pages in bvec are coalesced across a folio
bounary. The refcount of all non-slab folios should be increased to
ensure p9_releas_pages can put them correctly.

BUG: Bad page state in process md5sum  pfn:18300
page: refcount:0 mapcount:0 mapping:00000000d5ad8e4e index:0x60 pfn:0x18300
head: order:0 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
aops:z_erofs_aops ino:30b0f dentry name(?):"GoogleExtServicesCn.apk"
flags: 0x100000000000041(locked|head|node=0|zone=1)
raw: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0
raw: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000
head: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0
head: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000
head: 0100000000000000 0000000000000000 ffffffffffffffff 0000000000000000
head: 0000000000000010 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
Call Trace:
 dump_stack_lvl+0x53/0x70
 bad_page+0xd4/0x220
 __free_pages_ok+0x76d/0xf30
 __folio_put+0x230/0x320
 p9_release_pages+0x179/0x1f0
 p9_virtio_zc_request+0xa2a/0x1230
 p9_client_zc_rpc.constprop.0+0x247/0x700
 p9_client_read_once+0x34d/0x810
 p9_client_read+0xf3/0x150
 v9fs_issue_read+0x111/0x360
 netfs_unbuffered_read_iter_locked+0x927/0x1390
 netfs_unbuffered_read_iter+0xa2/0xe0
 vfs_iocb_iter_read+0x2c7/0x460
 erofs_fileio_rq_submit+0x46b/0x5b0
 z_erofs_runqueue+0x1203/0x21e0
 z_erofs_readahead+0x579/0x8b0
 read_pages+0x19f/0xa70
 page_cache_ra_order+0x4ad/0xb80
 filemap_readahead.isra.0+0xe7/0x150
 filemap_get_pages+0x7aa/0x1890
 filemap_read+0x320/0xc80
 vfs_read+0x6c6/0xa30
 ksys_read+0xf9/0x1c0
 do_syscall_64+0x9e/0x1a0
 entry_SYSCALL_64_after_hwframe+0x71/0x79

Fixes: b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page")
Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
---
 lib/iov_iter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
v2:
  * update commit message
  * update coding style

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 8c7fdb7d8c8f..bc9391e55d57 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1191,7 +1191,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
 			return -ENOMEM;
 		p = *pages;
 		for (int k = 0; k < n; k++) {
-			struct folio *folio = page_folio(page);
+			struct folio *folio = page_folio(page + k);
 			p[k] = page + k;
 			if (!folio_test_slab(folio))
 				folio_get(folio);
-- 
2.43.0

Re: [PATCH v2] lib/iov_iter: fix to increase non slab folio refcount

Posted by Vlastimil Babka 2 days, 19 hours ago

On 4/1/25 16:47, Sheng Yong wrote:
> From: Sheng Yong <shengyong1@xiaomi.com>
> 
> When testing EROFS file-backed mount over v9fs on qemu, I encountered
> a folio UAF issue. The page sanity check reports the following call
> trace. The root cause is that pages in bvec are coalesced across a folio
> bounary. The refcount of all non-slab folios should be increased to
> ensure p9_releas_pages can put them correctly.
> 
> BUG: Bad page state in process md5sum  pfn:18300
> page: refcount:0 mapcount:0 mapping:00000000d5ad8e4e index:0x60 pfn:0x18300
> head: order:0 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> aops:z_erofs_aops ino:30b0f dentry name(?):"GoogleExtServicesCn.apk"
> flags: 0x100000000000041(locked|head|node=0|zone=1)
> raw: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0
> raw: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000
> head: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0
> head: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000
> head: 0100000000000000 0000000000000000 ffffffffffffffff 0000000000000000
> head: 0000000000000010 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> Call Trace:
>  dump_stack_lvl+0x53/0x70
>  bad_page+0xd4/0x220
>  __free_pages_ok+0x76d/0xf30
>  __folio_put+0x230/0x320
>  p9_release_pages+0x179/0x1f0
>  p9_virtio_zc_request+0xa2a/0x1230
>  p9_client_zc_rpc.constprop.0+0x247/0x700
>  p9_client_read_once+0x34d/0x810
>  p9_client_read+0xf3/0x150
>  v9fs_issue_read+0x111/0x360
>  netfs_unbuffered_read_iter_locked+0x927/0x1390
>  netfs_unbuffered_read_iter+0xa2/0xe0
>  vfs_iocb_iter_read+0x2c7/0x460
>  erofs_fileio_rq_submit+0x46b/0x5b0
>  z_erofs_runqueue+0x1203/0x21e0
>  z_erofs_readahead+0x579/0x8b0
>  read_pages+0x19f/0xa70
>  page_cache_ra_order+0x4ad/0xb80
>  filemap_readahead.isra.0+0xe7/0x150
>  filemap_get_pages+0x7aa/0x1890
>  filemap_read+0x320/0xc80
>  vfs_read+0x6c6/0xa30
>  ksys_read+0xf9/0x1c0
>  do_syscall_64+0x9e/0x1a0
>  entry_SYSCALL_64_after_hwframe+0x71/0x79
> 
> Fixes: b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page")

Sigh. That went to v6.14

mm-hotfixes and Cc: stable then?

> Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

Thanks.

> ---
>  lib/iov_iter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> ---
> v2:
>   * update commit message
>   * update coding style
> 
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 8c7fdb7d8c8f..bc9391e55d57 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1191,7 +1191,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>  			return -ENOMEM;
>  		p = *pages;
>  		for (int k = 0; k < n; k++) {
> -			struct folio *folio = page_folio(page);
> +			struct folio *folio = page_folio(page + k);
>  			p[k] = page + k;
>  			if (!folio_test_slab(folio))
>  				folio_get(folio);

Re: [PATCH v2] lib/iov_iter: fix to increase non slab folio refcount

Posted by Sheng Yong 1 day, 21 hours ago

On 4/1/25 23:22, Vlastimil Babka wrote:
> On 4/1/25 16:47, Sheng Yong wrote:
>> From: Sheng Yong <shengyong1@xiaomi.com>
[...]
>>
>> Fixes: b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page")
> 
> Sigh. That went to v6.14
> 
> mm-hotfixes and Cc: stable then?

Hi, Vlastimil,

Shall I resend this patch with Cc: tag to the stable list?

thanks,
sheng

> 
>> Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
> 
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> 
> Thanks.
> 
>> ---
>>   lib/iov_iter.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>> ---
>> v2:
>>    * update commit message
>>    * update coding style
>>
>> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
>> index 8c7fdb7d8c8f..bc9391e55d57 100644
>> --- a/lib/iov_iter.c
>> +++ b/lib/iov_iter.c
>> @@ -1191,7 +1191,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>>   			return -ENOMEM;
>>   		p = *pages;
>>   		for (int k = 0; k < n; k++) {
>> -			struct folio *folio = page_folio(page);
>> +			struct folio *folio = page_folio(page + k);
>>   			p[k] = page + k;
>>   			if (!folio_test_slab(folio))
>>   				folio_get(folio);
>

Re: [PATCH v2] lib/iov_iter: fix to increase non slab folio refcount

Posted by Vlastimil Babka 1 day, 21 hours ago

On 4/2/25 15:36, Sheng Yong wrote:
> On 4/1/25 23:22, Vlastimil Babka wrote:
>> On 4/1/25 16:47, Sheng Yong wrote:
>>> From: Sheng Yong <shengyong1@xiaomi.com>
> [...]
>>>
>>> Fixes: b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page")
>> 
>> Sigh. That went to v6.14
>> 
>> mm-hotfixes and Cc: stable then?
> 
> Hi, Vlastimil,

Hi,

> Shall I resend this patch with Cc: tag to the stable list?

Andrew can do it when picking up the patch so no need to. Thanks.

> thanks,
> sheng
> 
>> 
>>> Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
>> 
>> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>> 
>> Thanks.
>> 
>>> ---
>>>   lib/iov_iter.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>> ---
>>> v2:
>>>    * update commit message
>>>    * update coding style
>>>
>>> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
>>> index 8c7fdb7d8c8f..bc9391e55d57 100644
>>> --- a/lib/iov_iter.c
>>> +++ b/lib/iov_iter.c
>>> @@ -1191,7 +1191,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>>>   			return -ENOMEM;
>>>   		p = *pages;
>>>   		for (int k = 0; k < n; k++) {
>>> -			struct folio *folio = page_folio(page);
>>> +			struct folio *folio = page_folio(page + k);
>>>   			p[k] = page + k;
>>>   			if (!folio_test_slab(folio))
>>>   				folio_get(folio);
>> 
>

Re: [PATCH v2] lib/iov_iter: fix to increase non slab folio refcount

Posted by Matthew Wilcox 2 days, 20 hours ago

On Tue, Apr 01, 2025 at 10:47:12PM +0800, Sheng Yong wrote:
> Fixes: b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page")
> Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>