From: Alban Crequy albancrequy@linux.microsoft.com
commit 8678ea06852cd1f819b870c773d43df888d15d46 upstream.
If a page fault occurs while copying the first byte, this function resets one byte before dst. As a consequence, an address could be modified and leaded to kernel crashes if case the modified address was accessed later.
Fixes: b58294ead14c ("maccess: allow architectures to provide kernel probing directly") Signed-off-by: Alban Crequy albancrequy@linux.microsoft.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Tested-by: Francis Laniel flaniel@linux.microsoft.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: stable@vger.kernel.org [5.8] Link: https://lore.kernel.org/bpf/20221110085614.111213-2-albancrequy@linux.micros... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/maccess.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/maccess.c +++ b/mm/maccess.c @@ -83,7 +83,7 @@ long strncpy_from_kernel_nofault(char *d return src - unsafe_addr; Efault: pagefault_enable(); - dst[-1] = '\0'; + dst[0] = '\0'; return -EFAULT; } #else /* HAVE_GET_KERNEL_NOFAULT */