Prevent freeing uninitialized pointer in compat_do_readv_writev
authorDan Rosenberg <drosenberg@vsecurity.com>
Wed, 22 Sep 2010 18:32:56 +0000 (14:32 -0400)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 23 Sep 2010 00:22:38 +0000 (17:22 -0700)
In 32-bit compatibility mode, the error handling for
compat_do_readv_writev() may free an uninitialized pointer, potentially
leading to all sorts of ugly memory corruption.  This is reliably
triggerable by unprivileged users by invoking the readv()/writev()
syscalls with an invalid iovec pointer.  The below patch fixes this to
emulate the non-compat version.

Introduced by commit b83733639a49 ("compat: factor out
compat_rw_copy_check_uvector from compat_do_readv_writev")

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Cc: stable@kernel.org (2.6.35)
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/compat.c

index 718c7062aec129844cda361e2f4b8a143aa31861..0644a154672b93012a4d7a7f864ba7f505b43213 100644 (file)
@@ -1153,7 +1153,7 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
 {
        compat_ssize_t tot_len;
        struct iovec iovstack[UIO_FASTIOV];
-       struct iovec *iov;
+       struct iovec *iov = iovstack;
        ssize_t ret;
        io_fn_t fn;
        iov_fn_t fnv;