ext4: fix infinite loop when replaying fast_commit

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix infinite loop when replaying fast_commit When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable. Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039. This commit fixes this issue by unconditionally initializing the structure in function ext4_es_find_extent_range(). Thanks to Zhang Yi, for figuring out the real problem!

References

• https://git.kernel.org/stable/c/5ed0496e383cb6de120e56991385dce70bbb87c1
• https://git.kernel.org/stable/c/0619f7750f2b178a1309808832ab20d85e0ad121
• https://git.kernel.org/stable/c/181e63cd595c688194e07332f9944b3a63193de2
• https://git.kernel.org/stable/c/c6e67df64783e99a657ef2b8c834ba2bf54c539c
• https://git.kernel.org/stable/c/81f819c537d29932e4b9267f02411cbc8b355178
• https://git.kernel.org/stable/c/907c3fe532253a6ef4eb9c4d67efb71fab58c706