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Subject[PATCH 3.18 37/93] mtd: jedec_probe: Fix crash in jedec_read_mfr()
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Walleij <linus.walleij@linaro.org>

commit 87a73eb5b56fd6e07c8e499fe8608ef2d8912b82 upstream.

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.

Fixes: 5c9c11e1c47c ("[MTD] [NOR] Add support for flash chips with ID in bank other than 0")
Cc: <stable@vger.kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/mtd/chips/jedec_probe.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/mtd/chips/jedec_probe.c
+++ b/drivers/mtd/chips/jedec_probe.c
@@ -1889,6 +1889,8 @@ static inline u32 jedec_read_mfr(struct
do {
uint32_t ofs = cfi_build_cmd_addr(0 + (bank << 8), map, cfi);
mask = (1 << (cfi->device_type * 8)) - 1;
+ if (ofs >= map->size)
+ return 0;
result = map_read(map, base + ofs);
bank++;
} while ((result.x[0] & mask) == CFI_MFR_CONTINUATION);

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