CVE-2026-64028 tracing: Avoid NULL return from hist_field_name() on truncation

In the Linux kernel, the following vulnerability has been resolved: tracing: Avoid NULL return from histfieldname on truncation histfieldname returns "" everywhere except the fully-qualified VARREF/EXPR case, where snprintf truncation returns NULL early and bypasses the bottom NULL-"" guard...

CVE-2026-64028 tracing: Avoid NULL return from hist_field_name() on truncation

In the Linux kernel, the following vulnerability has been resolved: tracing: Avoid NULL return from histfieldname on truncation histfieldname returns "" everywhere except the fully-qualified VARREF/EXPR case, where snprintf truncation returns NULL early and bypasses the bottom NULL-"" guard...