This backport patch addresses a NULL pointer dereference bug in 4.14.y BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 IP: i2cdev_ioctl_rdwr.isra.2+0xe4/0x360 PGD 13af50067 P4D 13af50067 PUD 13504c067 PMD 0 Oops: 0000 [#1] PREEMPT SMP Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 17421 Comm: rep Not tainted 4.14.295 #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 task: ffff88807c43a080 task.stack: ffffc90000d0c000 RIP: 0010:i2cdev_ioctl_rdwr.isra.2+0xe4/0x360 RSP: 0018:ffffc90000d0fdf0 EFLAGS: 00010297 RAX: ffff88807c43a080 RBX: 0000000000000000 RCX: 0000000000000000 .... Call Trace: i2cdev_ioctl+0x1a5/0x2a0 ? i2cdev_ioctl_rdwr.isra.2+0x360/0x360 do_vfs_ioctl+0xac/0x840 ? syscall_trace_enter+0x159/0x4a0 SyS_ioctl+0x7e/0xb0 do_syscall_64+0x8d/0x220 .... RIP: i2cdev_ioctl_rdwr.isra.2+0xe4/0x360 RSP: ffffc90000d0fdf0 .... Kernel panic - not syncing: Fatal exception Rebooting in 86400 seconds.. rdwr_pa[i].buf[0] is a NULL dereference when len=0, so to avoid dereferencing zero-length buffer we add a check on len before dereferencing. I have tested only with the reproducer and the bug doesnot occur after this patch. This patch is only made for 4.14.y as other higher LTS branches (>=4.19.y) already have the fix. Thanks, Harshit Alexander Popov (1): i2c: dev: prevent ZERO_SIZE_PTR deref in i2cdev_ioctl_rdwr() drivers/i2c/i2c-dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.37.1
