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[62.202.191.212]) by smtp.gmail.com with ESMTPSA id h19-20020a05600c351300b003a501ad8648sm6512770wmq.40.2022.08.05.18.46.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Aug 2022 18:46:08 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Martin KaFai Lau , Andrii Nakryiko , Daniel Borkmann Subject: [PATCH bpf v1 2/3] bpf: Don't reinit map value in prealloc_lru_pop Date: Sat, 6 Aug 2022 03:46:02 +0200 Message-Id: <20220806014603.1771-3-memxor@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220806014603.1771-1-memxor@gmail.com> References: <20220806014603.1771-1-memxor@gmail.com> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1290; i=memxor@gmail.com; h=from:subject; bh=MHKdHHusG/qo6mzxYxPwmqWOiQY6Z/3gwdT2miImhlw=; b=owEBbQKS/ZANAwAKAUzgyIZIvxHKAcsmYgBi7cfJ/+R0kgrOAnUcxhHBDF38yBHgeC9NNwm92kHk pFuhIsmJAjMEAAEKAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCYu3HyQAKCRBM4MiGSL8RygetEA DBf2BYiTCnGPdg/2awsfLls6gWj/5X9i2iczRnp8Q4xJ6b1NuhUQQnfpxL2FdfKcrW5smGn6/19DcM zVBF2KpUwnlHwGBZdZPesMeXT3YzyPqUQWre8zsKoKbV141f3wzBIeB5gm62H4Jw5FXGd97QtjhQoa hFM5+QHVgRn+nELDA+A4N03l53831unMdkE3yddykFkOdKOeboy7habpvnv95I8OPLjAGXG9wMav1D 4rYU88YbWrAplfU92JvVk0mw9lKLIGa1xVPNJMjQ7dWr4s3yM6wMnF/ckm1X9pgzEmJ2tX65y66D2z IaU8RyOrLfLmHD7dnKZcCoU2+DG9cGOotT2LI91dzeVDLFAGz89CFjCqsbTMe9psIOzqC/EhHIZ0Hn egUETGVpQZx2xovvWCjm5ST5rsEJkjItgGZtq3XKWkkvyQYD5XU7JZuNnt7CwsjoAkNV3Erjir7zkr zTDlaSdZhXgDnce6XSpYn/4RHAf+3atkkY1str+356mWD6BEzX7Q6eOkPLg5GBV7Ti7TOeXvcZfqRb rz6fcih870ZJLBVascGTDYxSGBgUyQQHnFaWj9R4v7Q9L81VMmFx75SEGslNGcYUomsDOL1rXBBOdq PvbCT9tJB3B21rE3s4kFiRVoyohGd2HW4q6Fq5USYYtoM+GU3dwVoz6IVF3A== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org The LRU map that is preallocated may have its elements reused while another program holds a pointer to it from bpf_map_lookup_elem. Hence, only check_and_free_fields is appropriate when the element is being deleted, as it ensures proper synchronization against concurrent access of the map value. After that, we cannot call check_and_init_map_value again as it may rewrite bpf_spin_lock, bpf_timer, and kptr fields while they can be concurrently accessed from a BPF program. Fixes: 68134668c17f ("bpf: Add map side support for bpf timers.") Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/hashtab.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index da7578426a46..4d793a92301b 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -311,12 +311,8 @@ static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key, struct htab_elem *l; if (node) { - u32 key_size = htab->map.key_size; - l = container_of(node, struct htab_elem, lru_node); - memcpy(l->key, key, key_size); - check_and_init_map_value(&htab->map, - l->key + round_up(key_size, 8)); + memcpy(l->key, key, htab->map.key_size); return l; } -- 2.34.1