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authorHugh Dickins <hughd@google.com>2012-03-28 14:42:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-28 17:14:35 -0700
commitd15cab975459fb6092eeba1be72c13621337784f (patch)
tree5c1d8d18c65a34eb738c97d75f2c44becdff1de3
parentmm, coredump: fail allocations when coredumping instead of oom killing (diff)
downloadlinux-dev-d15cab975459fb6092eeba1be72c13621337784f.tar.xz
linux-dev-d15cab975459fb6092eeba1be72c13621337784f.zip
swapon: check validity of swap_flags
Most system calls taking flags first check that the flags passed in are valid, and that helps userspace to detect when new flags are supported. But swapon never did so: start checking now, to help if we ever want to support more swap_flags in future. It's difficult to get stray bits set in an int, and swapon is not widely used, so this is most unlikely to break any userspace; but we can just revert if it turns out to do so. Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/swap.h3
-rw-r--r--mm/swapfile.c3
2 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index b86b5c20617d..8dc0ea7caf02 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -21,6 +21,9 @@ struct bio;
#define SWAP_FLAG_PRIO_SHIFT 0
#define SWAP_FLAG_DISCARD 0x10000 /* discard swap cluster after use */
+#define SWAP_FLAGS_VALID (SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \
+ SWAP_FLAG_DISCARD)
+
static inline int current_is_kswapd(void)
{
return current->flags & PF_KSWAPD;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index dae42f380d6e..fafc26d1b1dc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2022,6 +2022,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
struct page *page = NULL;
struct inode *inode = NULL;
+ if (swap_flags & ~SWAP_FLAGS_VALID)
+ return -EINVAL;
+
if (!capable(CAP_SYS_ADMIN))
return -EPERM;