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powerpc/rtas: use memmove for potentially overlapping buffer copy

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[ Upstream commit 271208ee5e335cb1ad280d22784940daf7ddf820 ]

Using memcpy() isn't safe when buf is identical to rtas_err_buf, which
can happen during boot before slab is up. Full context which may not
be obvious from the diff:

	if (altbuf) {
		buf = altbuf;
	} else {
		buf = rtas_err_buf;
		if (slab_is_available())
			buf = kmalloc(RTAS_ERROR_LOG_MAX, GFP_ATOMIC);
	}
	if (buf)
		memcpy(buf, rtas_err_buf, RTAS_ERROR_LOG_MAX);

This was found by inspection and I'm not aware of it causing problems
in practice. It appears to have been introduced by commit
033ef338b6 ("powerpc: Merge rtas.c into arch/powerpc/kernel"); the
old ppc64 version of this code did not have this problem.

Use memmove() instead.

Fixes: 033ef338b6 ("powerpc: Merge rtas.c into arch/powerpc/kernel")
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230220-rtas-queue-for-6-4-v1-2-010e4416f13f@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Nathan Lynch 2023-03-06 15:33:41 -06:00 committed by Greg Kroah-Hartman
parent 333a2a9846
commit ff3edfb3c8
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/kernel/rtas.c
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@ -398,7 +398,7 @@ static char *__fetch_rtas_last_error(char *altbuf)
buf = kmalloc(RTAS_ERROR_LOG_MAX, GFP_ATOMIC); buf = kmalloc(RTAS_ERROR_LOG_MAX, GFP_ATOMIC);
} }
if (buf) if (buf)
memcpy(buf, rtas_err_buf, RTAS_ERROR_LOG_MAX); memmove(buf, rtas_err_buf, RTAS_ERROR_LOG_MAX);
} }
return buf; return buf;