From a67632c8c2688d6e0091529bcefe54bc5ee80e9b Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 27 Aug 2026 14:43:03 +0100 Subject: cachefiles: Fix potential UAF/KASAN warning Currently, trace_cachefiles_coherency() is being passed a pointer to a __be64 lain over the coherency data in struct cachefiles_xattr so that it can display the first 8 bytes. However, the data is of variable length and could even be 0 bytes. This could lead to a UAF or KASAN warning. Fix this by making sure the buffer has room for at least 8 bytes and that those 8 bytes are pre-cleared. Further, those bytes are not 8-byte aligned, so fix the tracepoint to extract the data as four 2-byte words (they are 2-byte aligned) and reassemble the __be64. The compiler will convert this into a single 8-byte load where the CPU supports it. Fixes: 229105e5cfd9 ("cachefiles: Add auxiliary data trace") Link: https://sashiko.dev/#/patchset/20260810144746.574036-1-dhowells%40redhat.com Signed-off-by: David Howells Link: https://patch.msgid.link/20260827134304.2075713-11-dhowells@redhat.com Acked-by: Paulo Alcantara cc: Paulo Alcantara cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner (Amutable) --- include/trace/events/cachefiles.h | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h index 9259bc71049e..e3101410e8b2 100644 --- a/include/trace/events/cachefiles.h +++ b/include/trace/events/cachefiles.h @@ -372,7 +372,7 @@ TRACE_EVENT(cachefiles_rename, TRACE_EVENT(cachefiles_coherency, TP_PROTO(struct cachefiles_object *obj, ino_t ino, - u64 disk_aux, + const void *disk_aux, enum cachefiles_content content, enum cachefiles_coherency_trace why), @@ -389,12 +389,27 @@ TRACE_EVENT(cachefiles_coherency, ), TP_fast_assign( + union { + __be16 s[4]; + __be64 ll; + } x; + __entry->obj = obj->debug_id; __entry->why = why; __entry->content = content; __entry->ino = ino; __entry->aux = be64_to_cpup((__be64 *)obj->cookie->inline_aux); - __entry->disk_aux = disk_aux; + + /* cachefiles_xattr::data is 2-byte aligned but not 8-byte aligned. */ + if (disk_aux) { + x.s[0] = ((__be16 *)disk_aux)[0]; + x.s[1] = ((__be16 *)disk_aux)[1]; + x.s[2] = ((__be16 *)disk_aux)[2]; + x.s[3] = ((__be16 *)disk_aux)[3]; + __entry->disk_aux = be64_to_cpu(x.ll); + } else { + __entry->disk_aux = 0; + } ), TP_printk("o=%08x %s B=%llx c=%u aux=%llx dsk=%llx", -- cgit