Re: [PATCH 2/3] i2c: xiic: Prevent concurrent running of the IRQ handler and __xiic_start_xfer()

[Wolfram Sang <wsa@the-dreams.de>]

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On Mon, Nov 16, 2015 at 02:42:04PM +0100, Lars-Peter Clausen wrote:
> Prior to commit e6c9a037bc8a ("i2c: xiic: Remove the disabling of
> interrupts") IRQs where disabled when the initial __xiic_start_xfer() was
> called. After the commit the interrupt is enabled while the function is
> running, this means it is possible for the interrupt to be triggered while
> the function is still running. When this happens the internal data
> structures get corrupted and undefined behavior can occur like the
> following crash:
> 
> 	Internal error: Oops: 17 [#1] PREEMPT SMP ARM
> 	Modules linked in:
> 	CPU: 0 PID: 2040 Comm: i2cdetect Not tainted 4.0.0-02856-g047a308 #10956
> 	Hardware name: Xilinx Zynq Platform
> 	task: ee0c9500 ti: e99a2000 task.ti: e99a2000
> 	PC is at __xiic_start_xfer+0x6c4/0x7c8
> 	LR is at __xiic_start_xfer+0x690/0x7c8
> 	pc : [<c02bbffc>]    lr : [<c02bbfc8>]    psr: 800f0013
> 	sp : e99a3da8  ip : 00000000  fp : 00000000
> 	r10: 00000001  r9 : 600f0013  r8 : f0180000
> 	r7 : f0180000  r6 : c064e444  r5 : 00000017  r4 : ee031010
> 	r3 : 00000000  r2 : 00000000  r1 : 600f0013  r0 : 0000000f
> 	Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
> 	Control: 18c5387d  Table: 29a5404a  DAC: 00000015
> 	Process i2cdetect (pid: 2040, stack limit = 0xe99a2210)
> 	Stack: (0xe99a3da8 to 0xe99a4000)
> 	3da0:                   ee031010 00000000 00000001 ee031020 ee031224 c02bc5ec
> 	3dc0: ee34c604 00000000 ee0c9500 e99a3dcc e99a3dd0 e99a3dd0 e99a3dd8 c069f0e8
> 	3de0: 00000000 ee031020 c064e100 ffff90bb e99a3e48 c02b6590 ee031020 00000001
> 	3e00: e99a3e48 ee031020 00000000 e99a3e63 00000001 c02b6ec4 00000000 00000000
> 	3e20: 00000000 c02b7320 e99a3ef0 00000000 00000000 e99e3df0 00000000 00000000
> 	3e40: 00000103 2814575f 0000003e c00a0000 e99a3e85 0001003e ee0c0000 e99a3e63
> 	3e60: eefd3578 c064e61c ee0c9500 c0041e04 0000056c e9a56db8 00006e5a b6f5c000
> 	3e80: ee0c9548 eefd0040 00000001 eefd3540 ee0c9500 eefd39a0 c064b540 ee0c9500
> 	3ea0: 00000000 ee92b000 00000000 bef4862c ee34c600 e99ecdc0 00000720 00000003
> 	3ec0: e99a2000 00000000 00000000 c02b8b30 00000000 00000000 00000000 e99a3f24
> 	3ee0: b6e80000 00000000 00000000 c04257e8 00000000 e99a3f24 c02b8f08 00000703
> 	3f00: 00000003 c02116bc ee935300 00000000 bef4862c ee34c600 e99ecdc0 c02b91f0
> 	3f20: e99ecdc0 00000720 bef4862c eeb725f8 e99ecdc0 c00c9e2c 00000003 00000003
> 	3f40: ee248dc0 00000000 ee248dc8 00000002 eeb7c1a8 00000000 00000000 c00bb360
> 	3f60: 00000000 00000000 00000003 ee248dc0 bef4862c e99ecdc0 e99ecdc0 00000720
> 	3f80: 00000003 e99a2000 00000000 c00c9f68 00000000 00000000 b6f22000 00000036
> 	3fa0: c000dfa4 c000de20 00000000 00000000 00000003 00000720 bef4862c bef4862c
> 	3fc0: 00000000 00000000 b6f22000 00000036 00000000 00000000 b6f60000 00000000
> 	3fe0: 00013040 bef48614 00008cab b6ecdbe6 400f0030 00000003 2f7fd821 2f7fdc21
> 	[<c02bbffc>] (__xiic_start_xfer) from [<c02bc5ec>] (xiic_xfer+0x94/0x168)
> 	[<c02bc5ec>] (xiic_xfer) from [<c02b6590>] (__i2c_transfer+0x4c/0x7c)
> 	[<c02b6590>] (__i2c_transfer) from [<c02b6ec4>] (i2c_transfer+0x9c/0xc4)
> 	[<c02b6ec4>] (i2c_transfer) from [<c02b7320>] (i2c_smbus_xfer+0x3a0/0x4ec)
> 	[<c02b7320>] (i2c_smbus_xfer) from [<c02b8b30>] (i2cdev_ioctl_smbus+0xb0/0x214)
> 	[<c02b8b30>] (i2cdev_ioctl_smbus) from [<c02b91f0>] (i2cdev_ioctl+0xa0/0x1d4)
> 	[<c02b91f0>] (i2cdev_ioctl) from [<c00c9e2c>] (do_vfs_ioctl+0x4b0/0x5b8)
> 	[<c00c9e2c>] (do_vfs_ioctl) from [<c00c9f68>] (SyS_ioctl+0x34/0x5c)
> 	[<c00c9f68>] (SyS_ioctl) from [<c000de20>] (ret_fast_syscall+0x0/0x34)
> 	Code: e283300c e5843210 eafffe64 e5943210 (e1d320b4)
> 
> The issue can easily be reproduced by performing I2C access under high
> system load or IO load.
> 
> To fix the issue protect the invocation to __xiic_start_xfer() form
> xiic_start_xfer() with the same lock that is used to protect the interrupt
> handler.
> 
> Fixes: e6c9a037bc8a ("i2c: xiic: Remove the disabling of interrupts")
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

Applied to for-current, thanks!


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