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FAILED: patch "[PATCH] tracing/probes: Fix to record 0-length data_loc in" failed to apply to 6.1-stable tree

PATCH [email protected] 1 participant 1 message Jul 21, 2023

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The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 797311bce5c2ac90b8d65e357603cfd410d36ebb
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023072103-huff-flyable-0350@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

797311bce5c2 ("tracing/probes: Fix to record 0-length data_loc in fetch_store_string*() if fails") 4ed8f337dee3 ("Revert "tracing: Add "(fault)" name injection to kernel probes"") e38e2c6a9efc ("tracing/probes: Fix to update dynamic data counter if fetcharg uses it") 00cf3d672a9d ("tracing: Allow synthetic events to pass around stacktraces")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 797311bce5c2ac90b8d65e357603cfd410d36ebb Mon Sep 17 00:00:00 2001
From: "Masami Hiramatsu (Google)" <[email protected]>
Date: Tue, 11 Jul 2023 23:16:07 +0900
Subject: [PATCH] tracing/probes: Fix to record 0-length data_loc in
fetch_store_string*() if fails

Fix to record 0-length data to data_loc in fetch_store_string*() if it fails to get the string data.
Currently those expect that the data_loc is updated by store_trace_args() if it returns the error code. However, that does not work correctly if the argument is an array of strings. In that case, store_trace_args() only clears the first entry of the array (which may have no error) and leaves other entries. So it should be cleared by fetch_store_string*() itself. Also, 'dyndata' and 'maxlen' in store_trace_args() should be updated only if it is used (ret > 0 and argument is a dynamic data.)

Link https://lore.kernel.org/all/168908496683.123124.4761206188794205601.stgit@devnote2/ open here
Fixes 40b53b771806 ("tracing: probeevent: Add array type support")
Cc [email protected]
Reviewed-by Steven Rostedt (Google) <[email protected]>
Signed-off-by Masami Hiramatsu (Google) <[email protected]>
kernel/trace/trace_probe_kernel.h +9 -4
index 6deae2ce34f8..bb723eefd7b7 100644
@@ -37,6 +37,13 @@ fetch_store_strlen(unsigned long addr)
 	return (ret < 0) ? ret : len;
 }
 
+static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void *base)
+{
+	if (ret < 0)
+		ret = 0;
+	*(u32 *)dest = make_data_loc(ret, __dest - base);
+}
+
 /*
  * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
  * with max length and relative data location.

@@ -55,8 +62,7 @@ fetch_store_string_user(unsigned long addr, void *dest, void *base)
 	__dest = get_loc_data(dest, base);
 
 	ret = strncpy_from_user_nofault(__dest, uaddr, maxlen);
-	if (ret >= 0)
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
+	set_data_loc(ret, dest, __dest, base);
 
 	return ret;
 }

@@ -87,8 +93,7 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
 	 * probing.
 	 */
 	ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen);
-	if (ret >= 0)
-		*(u32 *)dest = make_data_loc(ret, __dest - base);
+	set_data_loc(ret, dest, __dest, base);
 
 	return ret;
 }
kernel/trace/trace_probe_tmpl.h +3 -7
index 185da001f4c3..3935b347f874 100644
@@ -267,13 +267,9 @@ store_trace_args(void *data, struct trace_probe *tp, void *rec,
 		if (unlikely(arg->dynamic))
 			*dl = make_data_loc(maxlen, dyndata - base);
 		ret = process_fetch_insn(arg->code, rec, dl, base);
-		if (arg->dynamic) {
-			if (unlikely(ret < 0)) {
-				*dl = make_data_loc(0, dyndata - base);
-			} else {
-				dyndata += ret;
-				maxlen -= ret;
-			}
+		if (arg->dynamic && likely(ret > 0)) {
+			dyndata += ret;
+			maxlen -= ret;
 		}
 	}
 }
kernel/trace/trace_uprobe.c +2 -1
index 8b92e34ff0c8..7b47e9a2c010 100644
@@ -170,7 +170,8 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
 			 */
 			ret++;
 		*(u32 *)dest = make_data_loc(ret, (void *)dst - base);
-	}
+	} else
+		*(u32 *)dest = make_data_loc(0, (void *)dst - base);
 
 	return ret;
 }