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authorMathias Krause <minipli@grsecurity.net>2022-01-27 16:02:18 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-02-03 18:45:39 +0300
commit46963e2e0629cb31c96b1d47ddd89dc3d8990b34 (patch)
tree75790bb0da32d9c87696b9983f05d244ac85adca /drivers/misc
parent26291c54e111ff6ba87a164d85d4a4e134b7315c (diff)
downloadlinux-46963e2e0629cb31c96b1d47ddd89dc3d8990b34.tar.xz
misc: fastrpc: avoid double fput() on failed usercopy
If the copy back to userland fails for the FASTRPC_IOCTL_ALLOC_DMA_BUFF ioctl(), we shouldn't assume that 'buf->dmabuf' is still valid. In fact, dma_buf_fd() called fd_install() before, i.e. "consumed" one reference, leaving us with none. Calling dma_buf_put() will therefore put a reference we no longer own, leading to a valid file descritor table entry for an already released 'file' object which is a straight use-after-free. Simply avoid calling dma_buf_put() and rely on the process exit code to do the necessary cleanup, if needed, i.e. if the file descriptor is still valid. Fixes: 6cffd79504ce ("misc: fastrpc: Add support for dmabuf exporter") Acked-by: Christian König <christian.koenig@amd.com> Signed-off-by: Mathias Krause <minipli@grsecurity.net> Link: https://lore.kernel.org/r/20220127130218.809261-1-minipli@grsecurity.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/misc')
-rw-r--r--drivers/misc/fastrpc.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 4ccbf43e6bfa..aa1682b94a23 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1288,7 +1288,14 @@ static int fastrpc_dmabuf_alloc(struct fastrpc_user *fl, char __user *argp)
}
if (copy_to_user(argp, &bp, sizeof(bp))) {
- dma_buf_put(buf->dmabuf);
+ /*
+ * The usercopy failed, but we can't do much about it, as
+ * dma_buf_fd() already called fd_install() and made the
+ * file descriptor accessible for the current process. It
+ * might already be closed and dmabuf no longer valid when
+ * we reach this point. Therefore "leak" the fd and rely on
+ * the process exit path to do any required cleanup.
+ */
return -EFAULT;
}