driver core: Fix a potential null-ptr-deref in module_add_driver()

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

driver core: Fix a potential null-ptr-deref in module_add_driver()

Inject fault while probing of-fpga-region, if kasprintf() fails in module_add_driver(), the second sysfs_remove_link() in exit path will cause null-ptr-deref as below because kernfs_name_hash() will call strlen() with NULL driver_name.

Fix it by releasing resources based on the exit path sequence.

KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [dfffffc000000000] address between user and kernel address ranges Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: of_fpga_region(+) fpga_region fpga_bridge cfg80211 rfkill 8021q garp mrp stp llc ipv6 [last unloaded: of_fpga_region] CPU: 2 UID: 0 PID: 2036 Comm: modprobe Not tainted 6.11.0-rc2-g6a0e38264012 #295 Hardware name: linux,dummy-virt (DT) pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : strlen+0x24/0xb0 lr : kernfs_name_hash+0x1c/0xc4 sp : ffffffc081f97380 x29: ffffffc081f97380 x28: ffffffc081f97b90 x27: ffffff80c821c2a0 x26: ffffffedac0be418 x25: 0000000000000000 x24: ffffff80c09d2000 x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000000 x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000001840 x17: 0000000000000000 x16: 0000000000000000 x15: 1ffffff8103f2e42 x14: 00000000f1f1f1f1 x13: 0000000000000004 x12: ffffffb01812d61d x11: 1ffffff01812d61c x10: ffffffb01812d61c x9 : dfffffc000000000 x8 : 0000004fe7ed29e4 x7 : ffffff80c096b0e7 x6 : 0000000000000001 x5 : ffffff80c096b0e0 x4 : 1ffffffdb990efa2 x3 : 0000000000000000 x2 : 0000000000000000 x1 : dfffffc000000000 x0 : 0000000000000000 Call trace: strlen+0x24/0xb0 kernfs_name_hash+0x1c/0xc4 kernfs_find_ns+0x118/0x2e8 kernfs_remove_by_name_ns+0x80/0x100 sysfs_remove_link+0x74/0xa8 module_add_driver+0x278/0x394 bus_add_driver+0x1f0/0x43c driver_register+0xf4/0x3c0 __platform_driver_register+0x60/0x88 of_fpga_region_init+0x20/0x1000 [of_fpga_region] do_one_initcall+0x110/0x788 do_init_module+0x1dc/0x5c8 load_module+0x3c38/0x4cac init_module_from_file+0xd4/0x128 idempotent_init_module+0x2cc/0x528 __arm64_sys_finit_module+0xac/0x100 invoke_syscall+0x6c/0x258 el0_svc_common.constprop.0+0x160/0x22c do_el0_svc+0x44/0x5c el0_svc+0x48/0xb8 el0t_64_sync_handler+0x13c/0x158 el0t_64_sync+0x190/0x194 Code: f2fbffe1 a90157f4 12000802 aa0003f5 (38e16861) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception