On ppc64le, When a string with PAGE_SIZE - 1 (i.e. 64k-1) length is
passed as a "filesystem type" argument to the mount(2) syscall,
copy_mount_string() ends up allocating 64k (the PAGE_SIZE on ppc64le)
worth of space for holding the string in kernel's address space.
Later, in set_precision() (invoked by get_fs_type() ->
__request_module() -> vsnprintf()), we end up assigning
strlen(fs-type-string) i.e. 65535 as the
value to 'struct printf_spec'->precision member. This field has a width
of 16 bits and it is a signed data type. Hence an invalid value ends
up getting assigned. This causes the "WARN_ONCE(spec->precision != prec,
"precision %d too large", prec)" statement inside set_precision() to be
executed.
This commit fixes the bug by validating the length of the "filesystem
type" argument passed to get_fs_type() function.
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
Reported-by: Abdul Haleem <abdhalee@xxxxxxxxxxxxxxxxxx>
Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
---
fs/filesystems.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/filesystems.c b/fs/filesystems.c
index 9135646e41ac..a61caf5b6ad3 100644
--- a/fs/filesystems.c
+++ b/fs/filesystems.c
@@ -268,6 +268,9 @@ struct file_system_type *get_fs_type(const char *name)
const char *dot = strchr(name, '.');
int len = dot ? dot - name : strlen(name);
+ if (len >= PATH_MAX)
+ return NULL;
+
fs = __get_fs_type(name, len);
if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
fs = __get_fs_type(name, len);
--
2.19.1
