talos-op-linux/fs/sysfs/file.c, branch v4.4.4

sysfs: correctly handle short reads on PREALLOC attrs.

2015-10-04T18:42:22+00:00

attributes declared with __ATTR_PREALLOC use sysfs_kf_read() which ignores the 'count' arg. So a 1-byte read request can return more bytes than that. This is seen with the 'dash' shell when 'read' is used on some 'md' sysfs attributes. So only return the 'min' of count and the attribute length. Signed-off-by: NeilBrown Acked-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

fs: sysfs: don't pass count == 0 to bin file readers

2015-06-01T01:17:17+00:00

If count == 0 bytes are requested by a reader, sysfs_kf_bin_read() deliberately returns 0 without passing a potentially harmful value to some externally defined underlying battr->read() function. However in case of (pos == size && count) the next clause always sets count to 0 and this value is handed over to battr->read(). The change intends to make obsolete (and remove later) a redundant sanity check in battr->read(), if it is present, or add more protection to struct bin_attribute users, who does not care about input arguments. Signed-off-by: Vladimir Zapolskiy Acked-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

kernfs: remove KERNFS_STATIC_NAME

2015-02-14T05:21:36+00:00

When a new kernfs node is created, KERNFS_STATIC_NAME is used to avoid making a separate copy of its name. It's currently only used for sysfs attributes whose filenames are required to stay accessible and unchanged. There are rare exceptions where these names are allocated and formatted dynamically but for the vast majority of cases they're consts in the rodata section. Now that kernfs is converted to use kstrdup_const() and kfree_const(), there's little point in keeping KERNFS_STATIC_NAME around. Remove it. Signed-off-by: Tejun Heo Cc: Andrzej Hajda Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sysfs/kernfs: make read requests on pre-alloc files use the buffer.

2014-11-07T18:54:38+00:00

To match the previous patch which used the pre-alloc buffer for writes, this patch causes reads to use the same buffer. This is not strictly necessary as the current seq_read() will allocate on first read, so user-space can trigger the required pre-alloc. But consistency is valuable. The read function is somewhat simpler than seq_read() and, for example, does not support reading from an offset into the file: reads must be at the start of the file. As seq_read() does not use the prealloc buffer, ->seq_show is incompatible with ->prealloc and caused an EINVAL return from open(). sysfs code which calls into kernfs always chooses the correct function. As the buffer is shared with writes and other reads, the mutex is extended to cover the copy_to_user. Signed-off-by: NeilBrown Reviewed-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

sysfs/kernfs: allow attributes to request write buffer be pre-allocated.

2014-11-07T18:53:25+00:00

md/raid allows metadata management to be performed in user-space. A various times, particularly on device failure, the metadata needs to be updated before further writes can be permitted. This means that the user-space program which updates metadata much not block on writeout, and so must not allocate memory. mlockall(MCL_CURRENT|MCL_FUTURE) and pre-allocation can avoid all memory allocation issues for user-memory, but that does not help kernel memory. Several kernel objects can be pre-allocated. e.g. files opened before any writes to the array are permitted. However some kernel allocation happens in places that cannot be pre-allocated. In particular, writes to sysfs files (to tell md that it can now allow writes to the array) allocate a buffer using GFP_KERNEL. This patch allows attributes to be marked as "PREALLOC". In that case the maximal buffer is allocated when the file is opened, and then used on each write instead of allocating a new buffer. As the same buffer is now shared for all writes on the same file description, the mutex is extended to cover full use of the buffer including the copy_from_user(). The new __ATTR_PREALLOC() 'or's a new flag in to the 'mode', which is inspected by sysfs_add_file_mode_ns() to determine if the file should be marked as requiring prealloc. Despite the comment, we *do* use ->seq_show together with ->prealloc in this patch. The next patch fixes that. Signed-off-by: NeilBrown Reviewed-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

fs: sysfs: return EGBIG on write if offset is larger than file size

2014-11-07T18:52:20+00:00

According to the user expectations common utilities like dd or sh redirection operator > should work correctly over binary files from sysfs. At the moment doing excessive write can not be completed: write(1, "\0\0\0\0\0\0\0\0", 8) = 4 write(1, "\0\0\0\0", 4) = 0 write(1, "\0\0\0\0", 4) = 0 write(1, "\0\0\0\0", 4) = 0 ... Fix the problem by returning EFBIG described in man 2 write. Signed-off-by: Vladimir Zapolskiy Cc: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

sysfs: make sure read buffer is zeroed

2014-05-20T01:15:53+00:00

13c589d5b0ac ("sysfs: use seq_file when reading regular files") switched sysfs from custom read implementation to seq_file to enable later transition to kernfs. After the change, the buffer passed to ->show() is acquired through seq_get_buf(); unfortunately, this introduces a subtle behavior change. Before the commit, the buffer passed to ->show() was always zero as it was allocated using get_zeroed_page(). Because seq_file doesn't clear buffers on allocation and neither does seq_get_buf(), after the commit, depending on the behavior of ->show(), we may end up exposing uninitialized data to userland thus possibly altering userland visible behavior and leaking information. Fix it by explicitly clearing the buffer. Signed-off-by: Tejun Heo Reported-by: Ron Fixes: 13c589d5b0ac ("sysfs: use seq_file when reading regular files") Cc: stable # 3.13+ Signed-off-by: Greg Kroah-Hartman

sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()

2014-04-16T18:56:33+00:00

All device_schedule_callback_owner() users are converted to use device_remove_file_self(). Remove now unused {sysfs|device}_schedule_callback_owner(). Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

Revert "sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()"

2014-03-26T03:54:57+00:00

This reverts commit d1ba277e79889085a2faec3b68b91ce89c63f888. As reported by Stephen, this patch breaks linux-next as a ppc patch suddenly (after 2 years) started using this old api call. So revert it for now, it will go away in 3.15-rc2 when we can change the PPC call to the new api. Reported-by: Stephen Rothwell Cc: Tejun Heo Cc: Stewart Smith Cc: Benjamin Herrenschmidt Signed-off-by: Greg Kroah-Hartman

sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()

2014-02-07T23:42:41+00:00