In the Linux kernel 5.0.21 and 5.3.11, mounting a crafted btrfs filesystem image, performing some operations, and then making a syncfs system call can lead to a use-after-free in try_merge_free_space in fs/btrfs/free-space-cache.c because the pointer to a left data structure can be the same as the pointer to a right data structure. A flaw was found in the Linux kernel's implementation of BTRFS free space management, where the kernel does not correctly manage the lifetime of internal data structures used. An attacker could use this flaw to corrupt memory or escalate privileges.
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