Merge tag 'v5.10-rc6' into patchwork

Linux 5.10-rc6

* tag 'v5.10-rc6': (1815 commits)
  Linux 5.10-rc6
  sock: set sk_err to ee_errno on dequeue from errq
  mptcp: fix NULL ptr dereference on bad MPJ
  net: openvswitch: fix TTL decrement action netlink message format
  perf probe: Change function definition check due to broken DWARF
  perf probe: Fix to die_entrypc() returns error correctly
  perf stat: Use proper cpu for shadow stats
  perf record: Synthesize cgroup events only if needed
  perf diff: Fix error return value in __cmd_diff()
  perf tools: Update copy of libbpf's hashmap.c
  x86/mce: Do not overwrite no_way_out if mce_end() fails
  kvm: x86/mmu: Fix get_mmio_spte() on CPUs supporting 5-level PT
  KVM: x86: Fix split-irqchip vs interrupt injection window request
  KVM: x86: handle !lapic_in_kernel case in kvm_cpu_*_extint
  usb: typec: stusb160x: fix power-opmode property with typec-power-opmode
  printk: finalize records with trailing newlines
  can: af_can: can_rx_unregister(): remove WARN() statement from list operation sanity check
  can: m_can: m_can_dev_setup(): add support for bosch mcan version 3.3.0
  can: m_can: fix nominal bitiming tseg2 min for version >= 3.1
  can: m_can: m_can_open(): remove IRQF_TRIGGER_FALLING from request_threaded_irq()'s flags
  ...

1 files changed, 17 insertions, 2 deletions

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index e6d5fcc2cdf3..122d8d0e253c 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -35,17 +35,32 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src,
 		goto byte_at_a_time;
 
 	while (max >= sizeof(unsigned long)) {
-		unsigned long c, data;
+		unsigned long c, data, mask;
 
 		/* Fall back to byte-at-a-time if we get a page fault */
 		unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time);
 
-		*(unsigned long *)(dst+res) = c;
+		/*
+		 * Note that we mask out the bytes following the NUL. This is
+		 * important to do because string oblivious code may read past
+		 * the NUL. For those routines, we don't want to give them
+		 * potentially random bytes after the NUL in `src`.
+		 *
+		 * One example of such code is BPF map keys. BPF treats map keys
+		 * as an opaque set of bytes. Without the post-NUL mask, any BPF
+		 * maps keyed by strings returned from strncpy_from_user() may
+		 * have multiple entries for semantically identical strings.
+		 */
 		if (has_zero(c, &data, &constants)) {
 			data = prep_zero_mask(c, data, &constants);
 			data = create_zero_mask(data);
+			mask = zero_bytemask(data);
+			*(unsigned long *)(dst+res) = c & mask;
 			return res + find_zero(data);
 		}
+
+		*(unsigned long *)(dst+res) = c;
+
 		res += sizeof(unsigned long);
 		max -= sizeof(unsigned long);
 	}