kernel.git/fs/jffs2/file.c, branch linux-6.4.y

jffs2: correct logic when creating a hole in jffs2_write_begin

2023-02-02T20:13:32Z

Bug description and fix: 1. Write data to a file, say all 1s from offset 0 to 16. 2. Truncate the file to a smaller size, say 8 bytes. 3. Write new bytes (say 2s) from an offset past the original size of the file, say at offset 20, for 4 bytes. This is supposed to create a "hole" in the file, meaning that the bytes from offset 8 (where it was truncated above) up to the new write at offset 20, should all be 0s (zeros). 4. Flush all caches using "echo 3 > /proc/sys/vm/drop_caches" (or unmount and remount) the f/s. 5. Check the content of the file. It is wrong. The 1s that used to be between bytes 9 and 16, before the truncation, have REAPPEARED (they should be 0s). We wrote a script and helper C program to reproduce the bug (reproduce_jffs2_write_begin_issue.sh, write_file.c, and Makefile). We can make them available to anyone. The above example is shown when writing a small file within the same first page. But the bug happens for larger files, as long as steps 1, 2, and 3 above all happen within the same page. The problem was traced to the jffs2_write_begin code, where it goes into an 'if' statement intended to handle writes past the current EOF (i.e., writes that may create a hole). The code computes a 'pageofs' that is the floor of the write position (pos), aligned to the page size boundary. In other words, 'pageofs' will never be larger than 'pos'. The code then sets the internal jffs2_raw_inode->isize to the size of max(current inode size, pageofs) but that is wrong: the new file size should be the 'pos', which is larger than both the current inode size and pageofs. Similarly, the code incorrectly sets the internal jffs2_raw_inode->dsize to the difference between the pageofs minus current inode size; instead it should be the current pos minus the current inode size. Finally, inode->i_size was also set incorrectly. The patch below fixes this bug. The bug was discovered using a new tool for finding f/s bugs using model checking, called MCFS (Model Checking File Systems). Signed-off-by: Yifei Liu Signed-off-by: Erez Zadok Signed-off-by: Manish Adkar Signed-off-by: Richard Weinberger

fs: rename current get acl method

2022-10-20T08:13:27Z

The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. The current inode operation for getting posix acls takes an inode argument but various filesystems (e.g., 9p, cifs, overlayfs) need access to the dentry. In contrast to the ->set_acl() inode operation we cannot simply extend ->get_acl() to take a dentry argument. The ->get_acl() inode operation is called from: acl_permission_check() -> check_acl() -> get_acl() which is part of generic_permission() which in turn is part of inode_permission(). Both generic_permission() and inode_permission() are called in the ->permission() handler of various filesystems (e.g., overlayfs). So simply passing a dentry argument to ->get_acl() would amount to also having to pass a dentry argument to ->permission(). We should avoid this unnecessary change. So instead of extending the existing inode operation rename it from ->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that passes a dentry argument and which filesystems that need access to the dentry can implement instead of ->get_inode_acl(). Filesystems like cifs which allow setting and getting posix acls but not using them for permission checking during lookup can simply not implement ->get_inode_acl(). This is intended to be a non-functional change. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Suggested-by/Inspired-by: Christoph Hellwig Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft)

fs: Change the type of filler_t

2022-05-09T20:36:48Z

By making filler_t the same as read_folio, we can use the same function for both in gfs2. We can push the use of folios down one more level in jffs2 and nfs. We also increase type safety for future users of the various read_cache_page() family of functions by forcing the parameter to be a pointer to struct file (or NULL). Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Reviewed-by: Andreas Gruenbacher

jffs2: Pass the file pointer to jffs2_do_readpage_unlock()

2022-05-09T20:28:41Z

In preparation for unifying the read_cache_page() and read_folio() implementations, make jffs2_do_readpage_unlock() get the inode from the page instead of passing it in from read_cache_page(). Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

jffs2: Convert jffs2 to read_folio

2022-05-09T20:21:45Z

This is a "weak" conversion which converts straight back to using pages. A full conversion should be performed at some point, hopefully by someone familiar with the filesystem. Signed-off-by: Matthew Wilcox (Oracle)

fs: Remove flags parameter from aops->write_begin

2022-05-08T18:28:19Z

There are no more aop flags left, so remove the parameter. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

fs: Remove aop flags parameter from grab_cache_page_write_begin()

2022-05-08T18:28:19Z

There are no more aop flags left, so remove the parameter. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

jffs2: GC deadlock reading a page that is used in jffs2_write_begin()

2021-12-23T21:33:41Z

GC task can deadlock in read_cache_page() because it may attempt to release a page that is actually allocated by another task in jffs2_write_begin(). The reason is that in jffs2_write_begin() there is a small window a cache page is allocated for use but not set Uptodate yet. This ends up with a deadlock between two tasks: 1) A task (e.g. file copy) - jffs2_write_begin() locks a cache page - jffs2_write_end() tries to lock "alloc_sem" from jffs2_reserve_space() <-- STUCK 2) GC task (jffs2_gcd_mtd3) - jffs2_garbage_collect_pass() locks "alloc_sem" - try to lock the same cache page in read_cache_page() <-- STUCK So to avoid this deadlock, hold "alloc_sem" in jffs2_write_begin() while reading data in a cache page. Signed-off-by: Kyeong Yoo Signed-off-by: Richard Weinberger

jffs2: Hook up splice_write callback

2021-04-15T20:01:14Z

overlayfs using jffs2 as the upper filesystem would fail in some cases since moving to v5.10. The test case used was to run 'touch' on a file that exists in the lower fs, causing the modification time to be updated. It returns EINVAL when the bug is triggered. A bisection showed this was introduced in v5.9-rc1, with commit 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops"). Reverting that commit restores the expected behaviour. Some digging showed that this was due to jffs2 lacking an implementation of splice_write. (For unknown reasons the warn_unsupported that should trigger was not displaying any output). Adding this patch resolved the issue and the test now passes. Cc: stable@vger.kernel.org Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") Signed-off-by: Joel Stanley Reviewed-by: Christoph Hellwig Tested-by: Lei YU Signed-off-by: Richard Weinberger

jffs2: pass the correct prototype to read_cache_page

2019-07-12T18:05:43Z

Fix the callback jffs2 passes to read_cache_page to actually have the proper type expected. Casting around function pointers can easily hide typing bugs, and defeats control flow protection. Link: http://lkml.kernel.org/r/20190520055731.24538-4-hch@lst.de Signed-off-by: Christoph Hellwig Reviewed-by: Kees Cook Cc: Nick Desaulniers Cc: Sami Tolvanen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds