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(-)
From: Alexander Popov alex.popov@linux.com
commit 23a27722b5292ef0b27403c87a109feea8296a5c upstream.
i2cdev_ioctl_rdwr() allocates i2c_msg.buf using memdup_user(), which returns ZERO_SIZE_PTR if i2c_msg.len is zero.
Currently i2cdev_ioctl_rdwr() always dereferences the buf pointer in case of I2C_M_RD | I2C_M_RECV_LEN transfer. That causes a kernel oops in case of zero len.
Let's check the len against zero before dereferencing buf pointer.
This issue was triggered by syzkaller.
Signed-off-by: Alexander Popov alex.popov@linux.com Reviewed-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de [wsa: use '< 1' instead of '!' for easier readability] Signed-off-by: Wolfram Sang wsa@the-dreams.de [Harshit: backport to 4.14.y, use rdwr_pa[i].len instead of msgs[i].len as the 4.14.y code uses rdwr_pa.] Signed-off-by: Harshit Mogalapalli harshit.m.mogalapalli@oracle.com --- Conflicts: drivers/i2c/i2c-dev.c - use rdwr_pa[i].len instead of msgs[i].len Since a NULL pointer dereference happens on 4.14.y this backport patch will fix the issue. --- drivers/i2c/i2c-dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index b7f9fb00f695..08aff5ebc99a 100644 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -297,7 +297,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client, */ if (rdwr_pa[i].flags & I2C_M_RECV_LEN) { if (!(rdwr_pa[i].flags & I2C_M_RD) || - rdwr_pa[i].buf[0] < 1 || + rdwr_pa[i].len < 1 || rdwr_pa[i].buf[0] < 1 || rdwr_pa[i].len < rdwr_pa[i].buf[0] + I2C_SMBUS_BLOCK_MAX) { i++;
linux-stable-mirror@lists.linaro.org
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Harshit Mogalapalli