[PATCH] mtd: jedec_probe: Fix crash in jedec_read_mfr()

[Linus Walleij]

On Sat, Mar 3, 2018 at 11:29 PM, Linus Walleij <linus.walleij at linaro.org> wrote:

> It turns out that the loop where we read manufacturer
> jedec_read_mfd() can under some circumstances get a
> CFI_MFR_CONTINUATION repeatedly, making the loop go
> over all banks and eventually hit the end of the
> map and crash because of an access violation:
>
> Unable to handle kernel paging request at virtual address c4980000
> pgd = (ptrval)
> [c4980000] *pgd=03808811, *pte=00000000, *ppte=00000000
> Internal error: Oops: 7 [#1] PREEMPT ARM
> CPU: 0 PID: 1 Comm: swapper Not tainted 4.16.0-rc1+ #150
> Hardware name: Gemini (Device Tree)
> PC is at jedec_probe_chip+0x6ec/0xcd0
> LR is at 0x4
> pc : [<c03a2bf4>]    lr : [<00000004>]    psr: 60000013
> sp : c382dd18  ip : 0000ffff  fp : 00000000
> r10: c0626388  r9 : 00020000  r8 : c0626340
> r7 : 00000000  r6 : 00000001  r5 : c3a71afc  r4 : c382dd70
> r3 : 00000001  r2 : c4900000  r1 : 00000002  r0 : 00080000
> Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> Control: 0000397f  Table: 00004000  DAC: 00000053
> Process swapper (pid: 1, stack limit = 0x(ptrval))
>
> Fix this by breaking the loop with a return 0 if
> the offset exceeds the map size.
>
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>

Could someone maintaining MTD please pick up this bug fix?

It is a very real problem to me.

Yours,
Linus Walleij