diff options
Diffstat (limited to 'meta/recipes-kernel/lttng/lttng-modules/0002-Fix-filter-interpreter-early-exits-on-uninitialized-.patch')
| -rw-r--r-- | meta/recipes-kernel/lttng/lttng-modules/0002-Fix-filter-interpreter-early-exits-on-uninitialized-.patch | 159 |
1 files changed, 0 insertions, 159 deletions
diff --git a/meta/recipes-kernel/lttng/lttng-modules/0002-Fix-filter-interpreter-early-exits-on-uninitialized-.patch b/meta/recipes-kernel/lttng/lttng-modules/0002-Fix-filter-interpreter-early-exits-on-uninitialized-.patch deleted file mode 100644 index 609690f05c..0000000000 --- a/meta/recipes-kernel/lttng/lttng-modules/0002-Fix-filter-interpreter-early-exits-on-uninitialized-.patch +++ /dev/null @@ -1,159 +0,0 @@ -From 23a2f61ffc6a656f136fa2044c0c3b8f79766779 Mon Sep 17 00:00:00 2001 -From: =?UTF-8?q?J=C3=A9r=C3=A9mie=20Galarneau?= - <jeremie.galarneau@efficios.com> -Date: Wed, 3 Mar 2021 18:52:19 -0500 -Subject: [PATCH 2/4] Fix: filter interpreter early-exits on uninitialized - value -MIME-Version: 1.0 -Content-Type: text/plain; charset=UTF-8 -Content-Transfer-Encoding: 8bit - -I observed that syscall filtering on string arguments wouldn't work on -my development machines, both running 5.11.2-arch1-1 (Arch Linux). - -For instance, enabling the tracing of the `openat()` syscall with the -'filename == "/proc/cpuinfo"' filter would not produce events even -though matching events were present in another session that had no -filtering active. The same problem occurred with `execve()`. - -I tried a couple of kernel versions before (5.11.1 and 5.10.13, if -memory serves me well) and I had the same problem. Meanwhile, I couldn't -reproduce the problem on various Debian machines (the LTTng CI) nor on a -fresh Ubuntu 20.04 with both the stock kernel and with an updated 5.11.2 -kernel. - -I built the lttng-modules with the interpreter debugging printout and -saw the following warning: - LTTng: [debug bytecode in /home/jgalar/EfficiOS/src/lttng-modules/src/lttng-bytecode-interpreter.c:bytecode_interpret@1508] Bytecode warning: loading a NULL string. - -After a shedload (yes, a _shed_load) of digging, I figured that the -problem was hidden in plain sight near that logging statement. - -In the `BYTECODE_OP_LOAD_FIELD_REF_USER_STRING` operation, the 'ax' -register's 'user_str' is initialized with the stack value (the user -space string's address in our case). However, a NULL check is performed -against the register's 'str' member. - -I initialy suspected that both members would be part of the same union -and alias each-other, but they are actually contiguous in a structure. - -On the unaffected machines, I could confirm that the `str` member was -uninitialized to a non-zero value causing the condition to evaluate to -false. - -Francis Deslauriers reproduced the problem by initializing the -interpreter stack to zero. - -I am unsure of the exact kernel configuration option that reveals this -issue on Arch Linux, but my kernel has the following option enabled: - -CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL: - Zero-initialize any stack variables that may be passed by reference - and had not already been explicitly initialized. This is intended to - eliminate all classes of uninitialized stack variable exploits and - information exposures. - -I have not tried to build without this enabled as, anyhow, this seems -to be a legitimate issue. - -I have spotted what appears to be an identical problem in -`BYTECODE_OP_LOAD_FIELD_REF_USER_SEQUENCE` and corrected it. However, -I have not exercised that code path. - -The commit that introduced this problem is 5b4ad89. - -The debug print-out of the `BYTECODE_OP_LOAD_FIELD_REF_USER_STRING` -operation is modified to print the user string (truncated to 31 chars). - -Upstream-status: backport - -Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com> -Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> -Change-Id: I2da3c31b9e3ce0e1b164cf3d2711c0893cbec273 ---- - lttng-filter-interpreter.c | 41 ++++++++++++++++++++++++++++++++++---- - 1 file changed, 37 insertions(+), 4 deletions(-) - -diff --git a/lttng-filter-interpreter.c b/lttng-filter-interpreter.c -index 5d572437..6e5a5139 100644 ---- a/lttng-filter-interpreter.c -+++ b/lttng-filter-interpreter.c -@@ -22,7 +22,7 @@ LTTNG_STACK_FRAME_NON_STANDARD(lttng_filter_interpret_bytecode); - * to handle user-space read. - */ - static --char get_char(struct estack_entry *reg, size_t offset) -+char get_char(const struct estack_entry *reg, size_t offset) - { - if (unlikely(offset >= reg->u.s.seq_len)) - return '\0'; -@@ -593,6 +593,39 @@ end: - return ret; - } - -+#ifdef DEBUG -+ -+#define DBG_USER_STR_CUTOFF 32 -+ -+/* -+ * In debug mode, print user string (truncated, if necessary). -+ */ -+static inline -+void dbg_load_ref_user_str_printk(const struct estack_entry *user_str_reg) -+{ -+ size_t pos = 0; -+ char last_char; -+ char user_str[DBG_USER_STR_CUTOFF]; -+ -+ pagefault_disable(); -+ do { -+ last_char = get_char(user_str_reg, pos); -+ user_str[pos] = last_char; -+ pos++; -+ } while (last_char != '\0' && pos < sizeof(user_str)); -+ pagefault_enable(); -+ -+ user_str[sizeof(user_str) - 1] = '\0'; -+ dbg_printk("load field ref user string: '%s%s'\n", user_str, -+ last_char != '\0' ? "[...]" : ""); -+} -+#else -+static inline -+void dbg_load_ref_user_str_printk(const struct estack_entry *user_str_reg) -+{ -+} -+#endif -+ - /* - * Return 0 (discard), or raise the 0x1 flag (log event). - * Currently, other flags are kept for future extensions and have no -@@ -1313,7 +1346,7 @@ uint64_t lttng_filter_interpret_bytecode(void *filter_data, - estack_push(stack, top, ax, bx); - estack_ax(stack, top)->u.s.user_str = - *(const char * const *) &filter_stack_data[ref->offset]; -- if (unlikely(!estack_ax(stack, top)->u.s.str)) { -+ if (unlikely(!estack_ax(stack, top)->u.s.user_str)) { - dbg_printk("Filter warning: loading a NULL string.\n"); - ret = -EINVAL; - goto end; -@@ -1322,7 +1355,7 @@ uint64_t lttng_filter_interpret_bytecode(void *filter_data, - estack_ax(stack, top)->u.s.literal_type = - ESTACK_STRING_LITERAL_TYPE_NONE; - estack_ax(stack, top)->u.s.user = 1; -- dbg_printk("ref load string %s\n", estack_ax(stack, top)->u.s.str); -+ dbg_load_ref_user_str_printk(estack_ax(stack, top)); - next_pc += sizeof(struct load_op) + sizeof(struct field_ref); - PO; - } -@@ -1340,7 +1373,7 @@ uint64_t lttng_filter_interpret_bytecode(void *filter_data, - estack_ax(stack, top)->u.s.user_str = - *(const char **) (&filter_stack_data[ref->offset - + sizeof(unsigned long)]); -- if (unlikely(!estack_ax(stack, top)->u.s.str)) { -+ if (unlikely(!estack_ax(stack, top)->u.s.user_str)) { - dbg_printk("Filter warning: loading a NULL sequence.\n"); - ret = -EINVAL; - goto end; --- -2.19.1 - |