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x86/fpu: Fix FPU state core dump truncation on CPUs with no extended xfeatures

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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: ba386777a3 ("x86/elf: Add a new FPU buffer layout info to x86 core files")
Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251210000219.4094353-2-yongxin.liu@windriver.com
This commit is contained in:
Yongxin Liu 2025-12-10 08:02:20 +08:00 committed by Ingo Molnar
parent 5288176a54
commit c8161e5304
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/fpu/xstate.c
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@ -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 */