7 - CVE-2025-22036

In the Linux kernel, the following vulnerability has been resolved:

exfat: fix random stack corruption after get_block

When get_block is called with a buffer_head allocated on the stack, such as do_mpage_readpage, stack corruption due to buffer_head UAF may occur in the following race condition situation.

mpage_read_folio
<>
do_mpage_readpage
exfat_get_block
bh_read
__bh_read
get_bh(bh)
submit_bh
wait_on_buffer
...
end_buffer_read_sync
__end_buffer_read_notouch
unlock_buffer
<>
...
...
...
... <>
.
. another_function
<>
put_bh(bh)
atomic_dec(bh->b_count)
* stack corruption here *

This patch returns -EAGAIN if a folio does not have buffers when bh_read needs to be called. By doing this, the caller can fallback to functions like block_read_full_folio(), create a buffer_head in the folio, and then call get_block again.

Let's do not call bh_read() with on-stack buffer_head.