1. copy_insn() doesn't look very nice, all calculations are
confusing and it is not immediately clear why do we read
the 2nd page first.
2. The usage of inode->i_size is wrong on 32-bit machines.
3. "Instruction at end of binary" logic is simply wrong, it
doesn't handle the case when uprobe->offset > inode->i_size.
In this case "bytes" overflows, and __copy_insn() writes to
the memory outside of uprobe->arch.insn.
Yes, uprobe_register() checks i_size_read(), but this file
can be truncated after that. All i_size checks are racy, we
do this only to catch the obvious mistakes.
Change copy_insn() to call __copy_insn() in a loop, simplify
and fix the bytes/nbytes calculations.
Note: we do not care if offset + size > i_size, the users of
arch_uprobe->insn can't know how many bytes were actually copied
anyway. But perhaps this needs more changes.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/events/uprobes.c | 47 +++++++++++++++++++++++------------------------
1 files changed, 23 insertions(+), 24 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index e615b78..db2802b 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -503,9 +503,8 @@ static bool consumer_del(struct uprobe *uprobe, struct
uprobe_consumer *uc)
return ret;
}
-static int
-__copy_insn(struct address_space *mapping, struct file *filp, char *insn,
- unsigned long nbytes, loff_t offset)
+static int __copy_insn(struct address_space *mapping, struct file *filp,
+ void *insn, int nbytes, loff_t offset)
{
struct page *page;
@@ -527,28 +526,28 @@ __copy_insn(struct address_space *mapping, struct file
*filp, char *insn,
static int copy_insn(struct uprobe *uprobe, struct file *filp)
{
- struct address_space *mapping;
- unsigned long nbytes;
- int bytes;
-
- nbytes = PAGE_SIZE - (uprobe->offset & ~PAGE_MASK);
- mapping = uprobe->inode->i_mapping;
+ struct address_space *mapping = uprobe->inode->i_mapping;
+ loff_t offs = uprobe->offset;
+ void *insn = uprobe->arch.insn;
+ int size = MAX_UINSN_BYTES;
+ int len, err = -EIO;
- /* Instruction at end of binary; copy only available bytes */
- if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
- bytes = uprobe->inode->i_size - uprobe->offset;
- else
- bytes = MAX_UINSN_BYTES;
+ do {
+ /* Copy only available bytes, but -EIO if nothing was read */
+ if (offs >= i_size_read(uprobe->inode))
+ break;
- /* Instruction at the page-boundary; copy bytes in second page */
- if (nbytes < bytes) {
- int err = __copy_insn(mapping, filp, uprobe->arch.insn + nbytes,
- bytes - nbytes, uprobe->offset + nbytes);
+ len = min_t(int, size, PAGE_SIZE - (offs & ~PAGE_MASK));
+ err = __copy_insn(mapping, filp, insn, len, offs);
if (err)
- return err;
- bytes = nbytes;
- }
- return __copy_insn(mapping, filp, uprobe->arch.insn, bytes,
uprobe->offset);
+ break;
+
+ insn += len;
+ offs += len;
+ size -= len;
+ } while (size);
+
+ return err;
}
static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
--
1.5.5.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
