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")
Cc: <stable@xxxxxxxxxxxxxxx> [5.8]
Signed-off-by: Alban Crequy <albancrequy@xxxxxxxxxxxxxxxxxxx>
Tested-by: Francis Laniel <flaniel@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Changes v1 to v2:
- add 'cc:stable', 'Fixes:' and review tag
- fix my email
- rebase on bpf tree and tag for bpf tree
---
mm/maccess.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/maccess.c b/mm/maccess.c
index 5f4d240f67ec..074f6b086671 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -97,7 +97,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
return src - unsafe_addr;
Efault:
pagefault_enable();
- dst[-1] = '\0';
+ dst[0] = '\0';
return -EFAULT;
}
--
2.36.1
