Avoid pgoff overflow in remap_file_pages
Thomas Pollet noticed that the remap_file_pages() system call in
fremap.c has a potential overflow in the first part of the if statement
below, which could cause it to process bogus input parameters.
Specifically the pgoff + size parameters could be wrap thereby
preventing the system call from failing when it should.
Reported-by: Thomas Pollet <thomas.pollet@gmail.com>
Signed-off-by: Larry Woodman <lwoodman@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/fremap.c b/mm/fremap.c
index 7b7f852..ec520c7 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -141,6 +141,10 @@
if (start + size <= start)
return err;
+ /* Does pgoff wrap? */
+ if (pgoff + (size >> PAGE_SHIFT) < pgoff)
+ return err;
+
/* Can we represent this offset inside this architecture's pte's? */
#if PTE_FILE_MAX_BITS < BITS_PER_LONG
if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))