From: Nathan Lynch nathanl@linux.ibm.com
[ 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 033ef338b6e0 ("powerpc: Merge rtas.c into arch/powerpc/kernel"); the old ppc64 version of this code did not have this problem.
Use memmove() instead.
Fixes: 033ef338b6e0 ("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.c... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/rtas.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index 31175b34856ac..9256cfaa8b6f1 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -981,7 +981,7 @@ static char *__fetch_rtas_last_error(char *altbuf) buf = kmalloc(RTAS_ERROR_LOG_MAX, GFP_ATOMIC); } if (buf) - memcpy(buf, rtas_err_buf, RTAS_ERROR_LOG_MAX); + memmove(buf, rtas_err_buf, RTAS_ERROR_LOG_MAX); }
return buf;