From: Alban Crequy <albancrequy@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Tested-by: Francis Laniel <flaniel@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.8]
Link: https://lore.kernel.org/bpf/20221110085614.111213-2-albancrequy@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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 */
