From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Ensure that file_seals is non-NULL before using it in the memfd_create()
syscall. One situation in which memfd_file_seals_ptr() could return a NULL
pointer is when CONFIG_SHMEM=n.
Cc: stable@xxxxxxxxxxxxxxx # 4.16.x
Fixes: 47b9012ecdc7 ("shmem: add sealing support to hugetlb-backed memfd")
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
mm/memfd.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/memfd.c b/mm/memfd.c
index 69b90c31d38..e763e76f110 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -371,12 +371,15 @@ SYSCALL_DEFINE2(memfd_create,
inode->i_mode &= ~0111;
file_seals = memfd_file_seals_ptr(file);
- *file_seals &= ~F_SEAL_SEAL;
- *file_seals |= F_SEAL_EXEC;
+ if (file_seals) {
+ *file_seals &= ~F_SEAL_SEAL;
+ *file_seals |= F_SEAL_EXEC;
+ }
} else if (flags & MFD_ALLOW_SEALING) {
/* MFD_EXEC and MFD_ALLOW_SEALING are set */
file_seals = memfd_file_seals_ptr(file);
- *file_seals &= ~F_SEAL_SEAL;
+ if (file_seals)
+ *file_seals &= ~F_SEAL_SEAL;
}
fd_install(fd, file);
--
2.25.1
