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29f0698532
Fix a bug in AFS read whereby the request page afs_read::index isn't incremented after calling ->page_done() if ->remain reaches 0, indicating that the data read is complete. Without this a NULL pointer exception happens when ->page_done() is called twice for the last page because the page clearing loop will call it also and afs_readpages_page_done() clears the current entry in the page list. BUG: unable to handle kernel NULL pointer dereference at (null) IP: afs_readpages_page_done+0x21/0xa4 [kafs] PGD 0 Oops: 0002 [#1] SMP Modules linked in: kafs(E) CPU: 2 PID: 3002 Comm: md5sum Tainted: G E 4.10.0-fscache #485 Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014 task: ffff8804017d86c0 task.stack: ffff8803fc1d8000 RIP: 0010:afs_readpages_page_done+0x21/0xa4 [kafs] RSP: 0018:ffff8803fc1db978 EFLAGS: 00010282 RAX: ffff880405d39af8 RBX: 0000000000000000 RCX: ffff880407d83ed4 RDX: 0000000000000000 RSI: ffff880405d39a00 RDI: ffff880405c6f400 RBP: ffff8803fc1db988 R08: 0000000000000000 R09: 0000000000000001 R10: ffff8803fc1db820 R11: ffff88040cf56000 R12: ffff8804088f1780 R13: ffff8804017d86c0 R14: ffff8804088f1780 R15: 0000000000003840 FS: 00007f8154469700(0000) GS:ffff88041fb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 00000004016ec000 CR4: 00000000001406e0 Call Trace: afs_deliver_fs_fetch_data+0x5b9/0x60e [kafs] ? afs_make_call+0x316/0x4e8 [kafs] ? afs_make_call+0x359/0x4e8 [kafs] afs_deliver_to_call+0x173/0x2e8 [kafs] ? afs_make_call+0x316/0x4e8 [kafs] afs_make_call+0x37a/0x4e8 [kafs] ? wake_up_q+0x4f/0x4f ? __init_waitqueue_head+0x36/0x49 afs_fs_fetch_data+0x21c/0x227 [kafs] ? afs_fs_fetch_data+0x21c/0x227 [kafs] afs_vnode_fetch_data+0xf3/0x1d2 [kafs] afs_readpages+0x314/0x3fd [kafs] __do_page_cache_readahead+0x208/0x2c5 ondemand_readahead+0x3a2/0x3b7 ? ondemand_readahead+0x3a2/0x3b7 page_cache_async_readahead+0x5e/0x67 generic_file_read_iter+0x23b/0x70c ? __inode_security_revalidate+0x2f/0x62 __vfs_read+0xc4/0xe8 vfs_read+0xd1/0x15a SyS_read+0x4c/0x89 do_syscall_64+0x80/0x191 entry_SYSCALL64_slow_path+0x25/0x25 Reported-by: Marc Dionne <marc.dionne@auristor.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Marc Dionne <marc.dionne@auristor.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.