[PATCH v6 01/13] buildid: Only consider GNU notes for build ID parsing

[Stephen Boyd <swboyd@chromium.org>]

Some kernel elf files have various notes that also happen to have an elf
note type of '3', which matches NT_GNU_BUILD_ID but the note name isn't
"GNU". For example, this note trips up the existing logic:

 Owner  Data size   Description
 Xen    0x00000008  Unknown note type: (0x00000003) description data: 00 00 00 ffffff80 ffffffff ffffffff ffffffff ffffffff

Let's make sure that it is a GNU note when parsing the build ID so that
we can use this function to parse a vmlinux's build ID too.

Reported-by: Petr Mladek <pmladek@suse.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Fixes: bd7525dacd7e ("bpf: Move stack_map_get_build_id into lib")
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 lib/buildid.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/buildid.c b/lib/buildid.c
index 6156997c3895..e014636ec3eb 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -31,6 +31,7 @@ static inline int parse_build_id(void *page_addr,
 
 		if (nhdr->n_type == BUILD_ID &&
 		    nhdr->n_namesz == sizeof("GNU") &&
+		    !strcmp((char *)(nhdr + 1), "GNU") &&
 		    nhdr->n_descsz > 0 &&
 		    nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
 			memcpy(build_id,
-- 
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