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authoryangerkun <yangerkun@huawei.com>2021-09-30 11:22:28 +0800
committerMiklos Szeredi <mszeredi@redhat.com>2021-10-29 13:48:19 +0200
commit9a254403760041528bc8f69fe2f5e1ef86950991 (patch)
tree8f18843e1fb6bf5cf3b9a9ab2ed6f91737c2eeb8 /fs/overlayfs
parent1dc1eed46f9fa4cb8a07baa24fb44c96d6dd35c9 (diff)
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ovl: fix use after free in struct ovl_aio_req
Example for triggering use after free in a overlay on ext4 setup: aio_read ovl_read_iter vfs_iter_read ext4_file_read_iter ext4_dio_read_iter iomap_dio_rw -> -EIOCBQUEUED /* * Here IO is completed in a separate thread, * ovl_aio_cleanup_handler() frees aio_req which has iocb embedded */ file_accessed(iocb->ki_filp); /**BOOM**/ Fix by introducing a refcount in ovl_aio_req similarly to aio_kiocb. This guarantees that iocb is only freed after vfs_read/write_iter() returns on underlying fs. Fixes: 2406a307ac7d ("ovl: implement async IO routines") Signed-off-by: yangerkun <yangerkun@huawei.com> Link: https://lore.kernel.org/r/20210930032228.3199690-3-yangerkun@huawei.com/ Cc: <stable@vger.kernel.org> # v5.6 Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
-rw-r--r--fs/overlayfs/file.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index c88ac571593d..44fea16751f1 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -17,6 +17,7 @@
struct ovl_aio_req {
struct kiocb iocb;
+ refcount_t ref;
struct kiocb *orig_iocb;
struct fd fd;
};
@@ -252,6 +253,14 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
return flags;
}
+static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
+{
+ if (refcount_dec_and_test(&aio_req->ref)) {
+ fdput(aio_req->fd);
+ kmem_cache_free(ovl_aio_request_cachep, aio_req);
+ }
+}
+
static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
{
struct kiocb *iocb = &aio_req->iocb;
@@ -268,8 +277,7 @@ static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
}
orig_iocb->ki_pos = iocb->ki_pos;
- fdput(aio_req->fd);
- kmem_cache_free(ovl_aio_request_cachep, aio_req);
+ ovl_aio_put(aio_req);
}
static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
@@ -319,7 +327,9 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
aio_req->orig_iocb = iocb;
kiocb_clone(&aio_req->iocb, iocb, real.file);
aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+ refcount_set(&aio_req->ref, 2);
ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
+ ovl_aio_put(aio_req);
if (ret != -EIOCBQUEUED)
ovl_aio_cleanup_handler(aio_req);
}
@@ -390,7 +400,9 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
kiocb_clone(&aio_req->iocb, iocb, real.file);
aio_req->iocb.ki_flags = ifl;
aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+ refcount_set(&aio_req->ref, 2);
ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
+ ovl_aio_put(aio_req);
if (ret != -EIOCBQUEUED)
ovl_aio_cleanup_handler(aio_req);
}