CVE-2024-39496

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

btrfs: zoned: fix use-after-free due to race with dev replace

While loading a zone's info during creation of a block group, we can race

with a device replace operation and then trigger a use-after-free on the

device that was just replaced (source device of the replace operation).

This happens because at btrfs_load_zone_info() we extract a device from

the chunk map into a local variable and then use the device while not

under the protection of the device replace rwsem. So if there's a device

replace operation happening when we extract the device and that device

is the source of the replace operation, we will trigger a use-after-free

if before we finish using the device the replace operation finishes and

frees the device.

Fix this by enlarging the critical section under the protection of the

device replace rwsem so that all uses of the device are done inside the

critical section.