From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- arch/alpha/lib/strcat.S | 55 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 arch/alpha/lib/strcat.S (limited to 'arch/alpha/lib/strcat.S') diff --git a/arch/alpha/lib/strcat.S b/arch/alpha/lib/strcat.S new file mode 100644 index 000000000..62b90ebbc --- /dev/null +++ b/arch/alpha/lib/strcat.S @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/lib/strcat.S + * Contributed by Richard Henderson (rth@tamu.edu) + * + * Append a null-terminated string from SRC to DST. + */ +#include + + .text + + .align 3 + .globl strcat + .ent strcat +strcat: + .frame $30, 0, $26 + .prologue 0 + + mov $16, $0 # set up return value + + /* Find the end of the string. */ + + ldq_u $1, 0($16) # load first quadword (a0 may be misaligned) + lda $2, -1 + insqh $2, $16, $2 + andnot $16, 7, $16 + or $2, $1, $1 + cmpbge $31, $1, $2 # bits set iff byte == 0 + bne $2, $found + +$loop: ldq $1, 8($16) + addq $16, 8, $16 + cmpbge $31, $1, $2 + beq $2, $loop + +$found: negq $2, $3 # clear all but least set bit + and $2, $3, $2 + + and $2, 0xf0, $3 # binary search for that set bit + and $2, 0xcc, $4 + and $2, 0xaa, $5 + cmovne $3, 4, $3 + cmovne $4, 2, $4 + cmovne $5, 1, $5 + addq $3, $4, $3 + addq $16, $5, $16 + addq $16, $3, $16 + + /* Now do the append. */ + + mov $26, $23 + br __stxcpy + + .end strcat +EXPORT_SYMBOL(strcat); -- cgit v1.3.1