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Subject[PATCH] Missing return value check on do_write_mem
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In drivers/char/mem.c do_write_mem can return -EFAULT but write_kmem forgets 
this and goes blindly.

Note: /dev/kmem can be written to only by root, so this *cannot* have security
implications.

Also, do_write_mem takes two unused params and is static - so I've removed
those. I actually double-checked this - however please test compilation on
Sparc/m68k, since there are some #ifdef.

CC me on replies as I'm not subscribed. Thanks.
--
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
--- ./drivers/char/mem.c.fix 2004-02-20 16:27:21.000000000 +0100
+++ ./drivers/char/mem.c 2004-03-08 12:17:23.000000000 +0100
@@ -96,13 +96,14 @@
}
#endif

-static ssize_t do_write_mem(struct file * file, void *p, unsigned long realp,
- const char * buf, size_t count, loff_t *ppos)
+static ssize_t do_write_mem(void *p, const char * buf, size_t count,
+ loff_t *ppos)
{
- ssize_t written;
+ ssize_t written = 0;

- written = 0;
#if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
+ unsigned long realp = *ppos;
+
/* we don't have page 0 mapped on sparc and m68k.. */
if (realp < PAGE_SIZE) {
unsigned long sz = PAGE_SIZE-realp;
@@ -165,7 +166,7 @@

if (!valid_phys_addr_range(p, &count))
return -EFAULT;
- return do_write_mem(file, __va(p), p, buf, count, ppos);
+ return do_write_mem(__va(p), buf, count, ppos);
}

static int mmap_mem(struct file * file, struct vm_area_struct * vma)
@@ -276,7 +277,9 @@
if (count > (unsigned long) high_memory - p)
wrote = (unsigned long) high_memory - p;

- wrote = do_write_mem(file, (void*)p, p, buf, wrote, ppos);
+ wrote = do_write_mem((void*)p, buf, wrote, ppos);
+ if (wrote < 0)
+ return wrote;

p += wrote;
buf += wrote;
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