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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2013-02-25 10:20:36 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-28 12:06:04 -0700
commitc18508394610b47964ef6c2d4d71b85873ce10fe (patch)
parent8fc39830ce6dc2a93f29872afce83b180a6d3deb (diff)
Fix: compat_rw_copy_check_uvector() misuse in aio, readv, writev, and security keys
commit 8aec0f5d4137532de14e6554fd5dd201ff3a3c49 upstream. Looking at mm/process_vm_access.c:process_vm_rw() and comparing it to compat_process_vm_rw() shows that the compatibility code requires an explicit "access_ok()" check before calling compat_rw_copy_check_uvector(). The same difference seems to appear when we compare fs/read_write.c:do_readv_writev() to fs/compat.c:compat_do_readv_writev(). This subtle difference between the compat and non-compat requirements should probably be debated, as it seems to be error-prone. In fact, there are two others sites that use this function in the Linux kernel, and they both seem to get it wrong: Now shifting our attention to fs/aio.c, we see that aio_setup_iocb() also ends up calling compat_rw_copy_check_uvector() through aio_setup_vectored_rw(). Unfortunately, the access_ok() check appears to be missing. Same situation for security/keys/compat.c:compat_keyctl_instantiate_key_iov(). I propose that we add the access_ok() check directly into compat_rw_copy_check_uvector(), so callers don't have to worry about it, and it therefore makes the compat call code similar to its non-compat counterpart. Place the access_ok() check in the same location where copy_from_user() can trigger a -EFAULT error in the non-compat code, so the ABI behaviors are alike on both compat and non-compat. While we are here, fix compat_do_readv_writev() so it checks for compat_rw_copy_check_uvector() negative return values. And also, fix a memory leak in compat_keyctl_instantiate_key_iov() error handling. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2 files changed, 9 insertions, 10 deletions
diff --git a/fs/compat.c b/fs/compat.c
index e5358c25e133..f77a963a5873 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -576,6 +576,10 @@ ssize_t compat_rw_copy_check_uvector(int type,
*ret_pointer = iov;
+ ret = -EFAULT;
+ if (!access_ok(VERIFY_READ, uvector, nr_segs*sizeof(*uvector)))
+ goto out;
* Single unix specification:
* We should -EINVAL if an element length is not >= 0 and fitting an
@@ -1106,17 +1110,12 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
if (!file->f_op)
goto out;
- ret = -EFAULT;
- if (!access_ok(VERIFY_READ, uvector, nr_segs*sizeof(*uvector)))
- goto out;
- tot_len = compat_rw_copy_check_uvector(type, uvector, nr_segs,
+ ret = compat_rw_copy_check_uvector(type, uvector, nr_segs,
UIO_FASTIOV, iovstack, &iov);
- if (tot_len == 0) {
- ret = 0;
+ if (ret <= 0)
goto out;
- }
+ tot_len = ret;
ret = rw_verify_area(type, file, pos, tot_len);
if (ret < 0)
goto out;
diff --git a/security/keys/compat.c b/security/keys/compat.c
index 338b510e9027..10a6e4c23401 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -40,12 +40,12 @@ long compat_keyctl_instantiate_key_iov(
iovstack, &iov);
if (ret < 0)
- return ret;
+ goto err;
if (ret == 0)
goto no_payload_free;
ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
if (iov != iovstack)
return ret;