Messages in this thread Patch in this message | | | From | Bjorn Helgaas <> | Subject | Re: [RFC] prevent "dd if=/dev/mem" crash | Date | Mon, 20 Oct 2003 11:42:26 -0600 |
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On Friday 17 October 2003 5:55 pm, Andrew Morton wrote: > Still, the code you have is quite reasonable. But please structure it > thusly: > ...
Here's a patch structured that way.
> As for return values: if the requested read or write starts at a > not-present address it should probably return -EFAULT. This is what ia32 > will do. Arguably this is indistinguishable from a bad address on the > userspace side and we should return -EINVAL but whatever.
I made it return -EFAULT. I worry a little bit because ia32 returned 0 (short read) when (addr >= high_memory) before, but I don't have a strong opinion one way or the other.
===== drivers/char/mem.c 1.44 vs edited ===== --- 1.44/drivers/char/mem.c Sun Sep 21 15:50:34 2003 +++ edited/drivers/char/mem.c Mon Oct 20 10:43:08 2003 @@ -79,6 +79,22 @@ #endif } +#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE +static inline int valid_phys_addr_range(unsigned long addr, size_t *count) +{ + unsigned long end_mem; + + end_mem = __pa(high_memory); + if (addr >= end_mem) + return 0; + + if (*count > end_mem - addr) + *count = end_mem - addr; + + return 1; +} +#endif + static ssize_t do_write_mem(struct file * file, void *p, unsigned long realp, const char * buf, size_t count, loff_t *ppos) { @@ -113,14 +129,10 @@ size_t count, loff_t *ppos) { unsigned long p = *ppos; - unsigned long end_mem; ssize_t read; - end_mem = __pa(high_memory); - if (p >= end_mem) - return 0; - if (count > end_mem - p) - count = end_mem - p; + if (!valid_phys_addr_range(p, &count)) + return -EFAULT; read = 0; #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU)) /* we don't have page 0 mapped on sparc and m68k.. */ @@ -149,13 +161,9 @@ size_t count, loff_t *ppos) { unsigned long p = *ppos; - unsigned long end_mem; - end_mem = __pa(high_memory); - if (p >= end_mem) - return 0; - if (count > end_mem - p) - count = end_mem - p; + if (!valid_phys_addr_range(p, &count)) + return -EFAULT; return do_write_mem(file, __va(p), p, buf, count, ppos); } - 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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