fs: dlm: fix invalid derefence of sb_lvbptr
In the Linux kernel, the following vulnerability has been resolved: fs: dlm: fix invalid derefence of sb_lvbptr I experience issues when putting a lkbsb on the stack and have sb_lvbptr field to a dangled pointer while not using DLM_LKF_VALBLK. It will crash with the following kernel message, the dangled pointer is here 0xdeadbeef as example: [ 102.749317] BUG: unable to handle page fault for address: 00000000deadbeef [ 102.749320] #PF: supervisor read access in kernel mode [ 102.749323] #PF: error_code(0x0000) - not-present page [ 102.749325] PGD 0 P4D 0 [ 102.749332] Oops: 0000 [#1] PREEMPT SMP PTI [ 102.749336] CPU: 0 PID: 1567 Com