Patch "perf tool: fix dereferencing NULL al->maps" 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 tool: fix dereferencing NULL al->maps

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-tool-fix-dereferencing-null-al-maps.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 e79632b2232d7ec08d58e5bf7da01b4194bf946f
Author: Casey Chen <cachen@xxxxxxxxxxxxxxx>
Date:   Mon Jul 22 15:15:48 2024 -0600

    perf tool: fix dereferencing NULL al->maps
    
    [ Upstream commit 4c17736689ccfc44ec7dcc472577f25c34cf8724 ]
    
    With 0dd5041c9a0e ("perf addr_location: Add init/exit/copy functions"),
    when cpumode is 3 (macro PERF_RECORD_MISC_HYPERVISOR),
    thread__find_map() could return with al->maps being NULL.
    
    The path below could add a callchain_cursor_node with NULL ms.maps.
    
    add_callchain_ip()
      thread__find_symbol(.., &al)
        thread__find_map(.., &al)   // al->maps becomes NULL
      ms.maps = maps__get(al.maps)
      callchain_cursor_append(..., &ms, ...)
        node->ms.maps = maps__get(ms->maps)
    
    Then the path below would dereference NULL maps and get segfault.
    
    fill_callchain_info()
      maps__machine(node->ms.maps);
    
    Fix it by checking if maps is NULL in fill_callchain_info().
    
    Fixes: 0dd5041c9a0e ("perf addr_location: Add init/exit/copy functions")
    Signed-off-by: Casey Chen <cachen@xxxxxxxxxxxxxxx>
    Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
    Reviewed-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
    Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
    Cc: yzhong@xxxxxxxxxxxxxxx
    Link: https://lore.kernel.org/r/20240722211548.61455-1-cachen@xxxxxxxxxxxxxxx
    Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index aee937d14fbbf..09e6b4e1401c9 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -1126,7 +1126,7 @@ int hist_entry__append_callchain(struct hist_entry *he, struct perf_sample *samp
 int fill_callchain_info(struct addr_location *al, struct callchain_cursor_node *node,
 			bool hide_unresolved)
 {
-	struct machine *machine = maps__machine(node->ms.maps);
+	struct machine *machine = node->ms.maps ? maps__machine(node->ms.maps) : NULL;
 
 	maps__put(al->maps);
 	al->maps = maps__get(node->ms.maps);