On Mon, Dec 08, 2014 at 07:28:17PM +0000, Al Viro wrote:
> On Mon, Dec 08, 2014 at 10:57:31AM -0800, Linus Torvalds wrote:
> > So the whole "get_page()" thing is broken. Iterating over pages in a
> > KVEC is simply wrong, wrong, wrong. It needs to fail.
>
> Well, _that_ is easy to do, of course... E.g. by replacing that thing in
> iov_iter_get_pages()/iov_iter_get_pages_alloc() with ({ return -EFAULT; })
> will do it.
OK, folded and pushed (i.e. in vfs.git#iov_iter and vfs.git#for-next).
Matches earlier behaviour; oops reproducer is easy -
dd if=/dev/zero of=foo.ko bs=4096 count=1
cat >a.c <<'EOF'
#define _GNU_SOURCE
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
main()
{
int fd = open("foo.ko", 00040000);
syscall(__NR_finit_module, fd, "", 0);
}
EOF
gcc a.c
strace ./a.out
Correct behaviour (both the mainline and this series with fixes folded):
open("foo.ko", O_RDONLY|O_DIRECT) = 3
finit_module(3, "", 0) = -1 EFAULT (Bad address)
Incorrect one:
open("foo.ko", O_RDONLY|O_DIRECT) = 3
finit_module(3, "", 0 <unfinished ...>
+++ killed by SIGKILL +++
Killed
with that oops reproduced. Not sure if it's a proper LTP or xfstests fodder,
but anyway, here it is.
Incremental from previous for-next is
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index e0605c1..a1599ca 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -560,15 +560,7 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
get_page(*pages = v.bv_page);
return v.bv_len;
}),({
- unsigned long addr = (unsigned long)v.iov_base, end;
- size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
-
- if (len > maxpages * PAGE_SIZE)
- len = maxpages * PAGE_SIZE;
- addr &= ~(PAGE_SIZE - 1);
- for (end = addr + len; addr < end; addr += PAGE_SIZE)
- get_page(*pages++ = virt_to_page(addr));
- return len - *start;
+ return -EFAULT;
})
)
return 0;
@@ -622,18 +614,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
get_page(*p = v.bv_page);
return v.bv_len;
}),({
- unsigned long addr = (unsigned long)v.iov_base, end;
- size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
- int n;
-
- addr &= ~(PAGE_SIZE - 1);
- n = DIV_ROUND_UP(len, PAGE_SIZE);
- *pages = p = get_pages_array(n);
- if (!p)
- return -ENOMEM;
- for (end = addr + len; addr < end; addr += PAGE_SIZE)
- get_page(*p++ = virt_to_page(addr));
- return len - *start;
+ return -EFAULT;
})
)
return 0;
--
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