Messages in this thread Patch in this message | | | Date | Thu, 6 Apr 2006 13:18:05 -0700 | From | "Randy.Dunlap" <> | Subject | [PATCH] mpparse: prevent table index out-of-bounds |
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On Thu, 6 Apr 2006 09:18:45 -0700 John Z. Bohach wrote:
Re: mem= causes oops (was Re: BIOS causes (exposes?) modprobe (load_module) kernel oops)
> I found the root cause, but don't know if its worth fixing. If the board has more than > 32 PCI busses on it, the mptable bus array will overwrite its bounds for the PCI busses, > and stomp on anything that's after it. In this case, what got stomped on is the PAGE_KERNEL_EXEC > variable, which changed the bit-field settings for the page tables (cleared the 'present' bit, > and screwed up the rest), hence accounting for the page fault.
Well, > 32 busses or just one busid value >= 32.
> This can only happen if there are more than 32 PCI busses, so I'd say its an _extremely_ rare > condition on a desktop system. At any rate, the fix would simply be to change the value of the > #define in the mptable.h header file (I forget which exactly, but its easy to find) from 32 to 256. > The side effect of that is that the kernel data area would grow, and mostly be a total waste, > since I can't fathom a desktop system with more than 32 PCI busses. On arch's where more than > 32 PCI busses are likely, the #define is already 256.
I think that the kernel init code should detect and prevent the data corruption. Here's a patch to do that, by ignoring busses whose busid value is too large. ~~~
From: Randy Dunlap <rdunlap@xenotime.net>
Prevent possible table overflow and unknown data corruption. Code is in an __init section so it will be discarded after init.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> --- arch/i386/kernel/mpparse.c | 7 +++++++ 1 files changed, 7 insertions(+)
--- linux-2617-rc1.orig/arch/i386/kernel/mpparse.c +++ linux-2617-rc1/arch/i386/kernel/mpparse.c @@ -249,6 +249,13 @@ static void __init MP_bus_info (struct m mpc_oem_bus_info(m, str, translation_table[mpc_record]); + if (m->mpc_busid >= MAX_MP_BUSSES) { + printk(KERN_WARNING "MP table busid value (%d) for bustype %s " + " is too large, max. supported is %d\n", + m->mpc_busid, str, MAX_MP_BUSSES - 1); + return; + } + if (strncmp(str, BUSTYPE_ISA, sizeof(BUSTYPE_ISA)-1) == 0) { mp_bus_id_to_type[m->mpc_busid] = MP_BUS_ISA; } else if (strncmp(str, BUSTYPE_EISA, sizeof(BUSTYPE_EISA)-1) == 0) { --- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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