7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Donggeun Yoo commit 443d23176812803d0fa182b8d05ef066a7b8271f upstream. DEFINE_HIST_FIELD_FN() reads a trace event field and widens it to the u64 the histogram uses as a key or a value: type *addr = (type *)(event + hist_field->field->offset); return (u64)(unsigned long)*addr; unsigned long is 32 bits on a 32-bit kernel, so the intermediate cast discards the upper half of a 64-bit field, and widens a signed field by zero extension from 32 bits rather than sign extension from its own width. Five of the eight instantiations are wrong there: s64, u64, s32, s16 and s8. The cast came in with commit 79e577cbce4c ("tracing: Support string type key properly"), which also added hist_field_dynstring() and hist_field_pstring(). Those convert a char * to u64 and do warn without an unsigned long in between on 32-bit. DEFINE_HIST_FIELD_FN() converts an integer and never a pointer, so it gains nothing from the cast and only loses information. Drop the intermediate cast and let the usual arithmetic conversions widen *addr according to its own type. unsigned long is 64 bits on LP64, so the two forms are identical there and 64-bit kernels are unaffected. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260917015532.103081-1-donggeunyoo.kernel@gmail.com Fixes: 79e577cbce4c ("tracing: Support string type key properly") Reported-by: sashiko-bot@kernel.org Closes: https://lore.kernel.org/all/20260914054614.82A9B1F000FF@smtp.kernel.org/ Signed-off-by: Donggeun Yoo Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_hist.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -466,7 +466,7 @@ static u64 hist_field_unary_minus(struct { \ type *addr = (type *)(event + hist_field->field->offset); \ \ - return (u64)(unsigned long)*addr; \ + return (u64)*addr; \ } DEFINE_HIST_FIELD_FN(s64);