diff mbox series

[v3,04/15] futex: Validate futex value against futex size

Message ID 20230921105247.828934099@noisy.programming.kicks-ass.net (mailing list archive)
State New
Headers show
Series futex: More futex2 bits | expand

Commit Message

Peter Zijlstra Sept. 21, 2023, 10:45 a.m. UTC 
Ensure the futex value fits in the given futex size. Since this adds a
constraint to an existing syscall, it might possibly change behaviour.

Currently the value would be truncated to a u32 and any high bits
would get silently lost.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/futex/futex.h    |   10 ++++++++++
 kernel/futex/syscalls.c |    3 +++
 2 files changed, 13 insertions(+)
diff mbox series

Patch

Index: linux-2.6/kernel/futex/futex.h
===================================================================
--- linux-2.6.orig/kernel/futex/futex.h
+++ linux-2.6/kernel/futex/futex.h
@@ -85,6 +85,16 @@  static inline bool futex_flags_valid(uns
 	return true;
 }
 
+static inline bool futex_validate_input(unsigned int flags, u64 val)
+{
+	int bits = 8 * futex_size(flags);
+
+	if (bits < 64 && (val >> bits))
+		return false;
+
+	return true;
+}
+
 #ifdef CONFIG_FAIL_FUTEX
 extern bool should_fail_futex(bool fshared);
 #else
Index: linux-2.6/kernel/futex/syscalls.c
===================================================================
--- linux-2.6.orig/kernel/futex/syscalls.c
+++ linux-2.6/kernel/futex/syscalls.c
@@ -209,6 +209,9 @@  static int futex_parse_waitv(struct fute
 		if (!futex_flags_valid(flags))
 			return -EINVAL;
 
+		if (!futex_validate_input(flags, aux.val))
+			return -EINVAL;
+
 		futexv[i].w.flags = flags;
 		futexv[i].w.val = aux.val;
 		futexv[i].w.uaddr = aux.uaddr;