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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc72aefc0a6sm1360118a12.28.2026.09.19.15.25.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 15:25:55 -0700 (PDT) From: Hui Peng To: luisbg@kernel.org, salah.triki@gmail.com, brauner@kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] befs: check NULL return from befs_bt_get_key() and fix keysize in befs_btree_read() Date: Sat, 19 Sep 2026 22:25:55 +0000 Message-ID: <20260919222555.3792599-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Fix two issues in fs/befs/: 1. In befs_btree_find() and befs_btree_read() (fs/befs/btree.c), check for a NULL return from befs_bt_get_key() when a corrupted B+tree node has out-of-bounds key offsets or lengths. 2. In befs_btree_read() and befs_readdir() (fs/befs/linuxvfs.c), set keysize from the actual copied string length rather than the raw buffer size so uninitialized stack bytes are not passed to filldir(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/fs/befs/btree.c b/fs/befs/btree.c index aa24f1daccdd..67633e5f27fe 100644 --- a/fs/befs/btree.c +++ b/fs/befs/btree.c @@ -219,6 +219,19 @@ befs_bt_read_node(struct super_block *sb, const befs_data_stream *ds, node->head.all_key_length = fs16_to_cpu(sb, node->od_node->all_key_length); + { + size_t keylen_off = round_up(sizeof(befs_btree_nodehead) + + node->head.all_key_length, 8); + size_t total_needed = keylen_off + + (size_t)node->head.all_key_count * (sizeof(fs16) + sizeof(fs64)); + if (off >= node->bh->b_size || + total_needed > node->bh->b_size - off) { + brelse(node->bh); + node->bh = NULL; + return BEFS_ERR; + } + } + befs_debug(sb, "<--- %s", __func__); return BEFS_OK; } @@ -343,6 +356,8 @@ befs_find_key(struct super_block *sb, struct befs_btree_node *node, /* if node can not contain key, just skip this node */ last = node->head.all_key_count - 1; thiskey = befs_bt_get_key(sb, node, last, &keylen); + if (!thiskey) + return BEFS_BT_NOT_FOUND; eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len); if (eq < 0) { @@ -360,6 +375,8 @@ befs_find_key(struct super_block *sb, struct befs_btree_node *node, befs_debug(sb, "first: %d, last: %d, mid: %d", first, last, mid); thiskey = befs_bt_get_key(sb, node, mid, &keylen); + if (!thiskey) + return BEFS_BT_NOT_FOUND; eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len); @@ -417,6 +434,7 @@ befs_btree_read(struct super_block *sb, const befs_data_stream *ds, int cur_key; fs64 *valarray; char *keystart; + ssize_t copy_len; u16 keylen; int res; @@ -487,6 +505,10 @@ befs_btree_read(struct super_block *sb, const befs_data_stream *ds, valarray = befs_bt_valarray(this_node); keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen); + if (!keystart) { + brelse(this_node->bh); + goto error_alloc; + } befs_debug(sb, "Read [%llu,%d]: keysize %d", (long long unsigned int)node_off, (int)cur_key, @@ -499,9 +521,9 @@ befs_btree_read(struct super_block *sb, const befs_data_stream *ds, goto error_alloc; } - strscpy(keybuf, keystart, keylen + 1); + copy_len = strscpy(keybuf, keystart, keylen + 1); + *keysize = (copy_len < 0) ? keylen : copy_len; *value = fs64_to_cpu(sb, valarray[cur_key]); - *keysize = keylen; befs_debug(sb, "Read [%llu,%d]: Key \"%.*s\", Value %llu", node_off, cur_key, keylen, keybuf, *value); @@ -678,7 +700,7 @@ befs_bt_get_key(struct super_block *sb, struct befs_btree_node *node, char *keystart; fs16 *keylen_index; - if (index < 0 || index > node->head.all_key_count) { + if (index < 0 || index >= node->head.all_key_count) { *keylen = 0; return NULL; } @@ -691,6 +713,12 @@ befs_bt_get_key(struct super_block *sb, struct befs_btree_node *node, else prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]); + if (fs16_to_cpu(sb, keylen_index[index]) < prev_key_end || + fs16_to_cpu(sb, keylen_index[index]) > node->head.all_key_length) { + *keylen = 0; + return NULL; + } + *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end; return keystart + prev_key_end; diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c index ee0cbae521b9..de3be4d61c80 100644 --- a/fs/befs/linuxvfs.c +++ b/fs/befs/linuxvfs.c @@ -222,7 +222,7 @@ befs_readdir(struct file *file, struct dir_context *ctx) befs_off_t value; int result; size_t keysize; - char keybuf[BEFS_NAME_LEN + 1]; + char keybuf[BEFS_NAME_LEN + 1] = { 0 }; befs_debug(sb, "---> %s name %pD, inode %llu, ctx->pos %lld", __func__, file, inode->i_ino, ctx->pos);