From: Yongxin Liu Date: Wed, 10 Dec 2025 00:02:20 +0000 (+0800) Subject: x86/fpu: Fix FPU state core dump truncation on CPUs with no extended xfeatures X-Git-Tag: v6.19-rc2~4^2~7 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c8161e5304abb26e6c0bec6efc947992500fa6c5;p=thirdparty%2Fkernel%2Flinux.git x86/fpu: Fix FPU state core dump truncation on CPUs with no extended xfeatures Zero can be a valid value of num_records. For example, on Intel Atom x6425RE, only x87 and SSE are supported (features 0, 1), and fpu_user_cfg.max_features is 3. The for_each_extended_xfeature() loop only iterates feature 2, which is not enabled, so num_records = 0. This is valid and should not cause core dump failure. The issue is that dump_xsave_layout_desc() returns 0 for both genuine errors (dump_emit() failure) and valid cases (no extended features). Use negative return values for errors and only abort on genuine failures. Fixes: ba386777a30b ("x86/elf: Add a new FPU buffer layout info to x86 core files") Signed-off-by: Yongxin Liu Signed-off-by: Ingo Molnar Link: https://patch.msgid.link/20251210000219.4094353-2-yongxin.liu@windriver.com --- diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 48113c5193aa..76153dfb58c9 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1946,7 +1946,7 @@ static int dump_xsave_layout_desc(struct coredump_params *cprm) }; if (!dump_emit(cprm, &xc, sizeof(xc))) - return 0; + return -1; num_records++; } @@ -1984,7 +1984,7 @@ int elf_coredump_extra_notes_write(struct coredump_params *cprm) return 1; num_records = dump_xsave_layout_desc(cprm); - if (!num_records) + if (num_records < 0) return 1; /* Total size should be equal to the number of records */