Patch "perf machine: Avoid out of bounds LBR memory read" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    perf machine: Avoid out of bounds LBR memory read

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-machine-avoid-out-of-bounds-lbr-memory-read.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit bb269fae402812c24abf53e9514e2938059a350d
Author: Ian Rogers <irogers@xxxxxxxxxx>
Date:   Tue Oct 24 15:23:05 2023 -0700

    perf machine: Avoid out of bounds LBR memory read
    
    [ Upstream commit ab8ce150781d326c6bfbe1e09f175ffde1186f80 ]
    
    Running perf top with address sanitizer and "--call-graph=lbr" fails
    due to reading sample 0 when no samples exist. Add a guard to prevent
    this.
    
    Fixes: e2b23483eb1d ("perf machine: Factor out lbr_callchain_add_lbr_ip()")
    Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
    Cc: K Prateek Nayak <kprateek.nayak@xxxxxxx>
    Cc: Ravi Bangoria <ravi.bangoria@xxxxxxx>
    Cc: Sandipan Das <sandipan.das@xxxxxxx>
    Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
    Cc: German Gomez <german.gomez@xxxxxxx>
    Cc: James Clark <james.clark@xxxxxxx>
    Cc: Nick Terrell <terrelln@xxxxxx>
    Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
    Cc: Changbin Du <changbin.du@xxxxxxxxxx>
    Cc: liuwenyu <liuwenyu7@xxxxxxxxxx>
    Cc: Yang Jihong <yangjihong1@xxxxxxxxxx>
    Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
    Cc: Miguel Ojeda <ojeda@xxxxxxxxxx>
    Cc: Song Liu <song@xxxxxxxxxx>
    Cc: Leo Yan <leo.yan@xxxxxxxxxx>
    Cc: Kajol Jain <kjain@xxxxxxxxxxxxx>
    Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
    Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
    Cc: Athira Rajeev <atrajeev@xxxxxxxxxxxxxxxxxx>
    Cc: Yanteng Si <siyanteng@xxxxxxxxxxx>
    Cc: Liam Howlett <liam.howlett@xxxxxxxxxx>
    Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20231024222353.3024098-3-irogers@xxxxxxxxxx
    Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 88f31b3a63acb..e6a8d758f6fe4 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -2624,16 +2624,18 @@ static int lbr_callchain_add_lbr_ip(struct thread *thread,
 		save_lbr_cursor_node(thread, cursor, i);
 	}
 
-	/* Add LBR ip from first entries.to */
-	ip = entries[0].to;
-	flags = &entries[0].flags;
-	*branch_from = entries[0].from;
-	err = add_callchain_ip(thread, cursor, parent,
-			       root_al, &cpumode, ip,
-			       true, flags, NULL,
-			       *branch_from);
-	if (err)
-		return err;
+	if (lbr_nr > 0) {
+		/* Add LBR ip from first entries.to */
+		ip = entries[0].to;
+		flags = &entries[0].flags;
+		*branch_from = entries[0].from;
+		err = add_callchain_ip(thread, cursor, parent,
+				root_al, &cpumode, ip,
+				true, flags, NULL,
+				*branch_from);
+		if (err)
+			return err;
+	}
 
 	return 0;
 }