linux-kernel - [PATCH 4.10 010/110] staging: android: ashmem: lseek failed due to no FMODE

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Date:   Mon, 10 Apr 2017 18:42:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Shuxiao Zhang <zhangshuxiao@...omi.com>,
        Greg Hackmann <ghackmann@...gle.com>
Subject: [PATCH 4.10 010/110] staging: android: ashmem: lseek failed due to no FMODE_LSEEK.

4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Shuxiao Zhang <zhangshuxiao@...omi.com>

commit 97fbfef6bd597888485b653175fb846c6998b60c upstream.

vfs_llseek will check whether the file mode has
FMODE_LSEEK, no return failure. But ashmem can be
lseek, so add FMODE_LSEEK to ashmem file.

Comment From Greg Hackmann:
	ashmem_llseek() passes the llseek() call through to the backing
	shmem file.  91360b02ab48 ("ashmem: use vfs_llseek()") changed
	this from directly calling the file's llseek() op into a VFS
	layer call.  This also adds a check for the FMODE_LSEEK bit, so
	without that bit ashmem_llseek() now always fails with -ESPIPE.

Fixes: 91360b02ab48 ("ashmem: use vfs_llseek()")
Signed-off-by: Shuxiao Zhang <zhangshuxiao@...omi.com>
Tested-by: Greg Hackmann <ghackmann@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/android/ashmem.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -409,6 +409,7 @@ static int ashmem_mmap(struct file *file
 			ret = PTR_ERR(vmfile);
 			goto out;
 		}
+		vmfile->f_mode |= FMODE_LSEEK;
 		asma->file = vmfile;
 	}
 	get_file(asma->file);