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Zhihao Cheng
6379b44cdc
For error handling path in ubifs_symlink(), inode will be marked as
bad first, then iput() is invoked. If inode->i_link is initialized by
fscrypt_encrypt_symlink() in encryption scenario, inode->i_link won't
be freed by callchain ubifs_free_inode -> fscrypt_free_inode in error
handling path, because make_bad_inode() has changed 'inode->i_mode' as
'S_IFREG'.
Following kmemleak is easy to be reproduced by injecting error in
ubifs_jnl_update() when doing symlink in encryption scenario:
unreferenced object 0xffff888103da3d98 (size 8):
comm "ln", pid 1692, jiffies 4294914701 (age 12.045s)
backtrace:
kmemdup+0x32/0x70
__fscrypt_encrypt_symlink+0xed/0x1c0
ubifs_symlink+0x210/0x300 [ubifs]
vfs_symlink+0x216/0x360
do_symlinkat+0x11a/0x190
do_syscall_64+0x3b/0xe0
There are two ways fixing it:
1. Remove make_bad_inode() in error handling path. We can do that
because ubifs_evict_inode() will do same processes for good
symlink inode and bad symlink inode, for inode->i_nlink checking
is before is_bad_inode().
2. Free inode->i_link before marking inode bad.
Method 2 is picked, it has less influence, personally, I think.
Cc: stable@vger.kernel.org
Fixes: 2c58d548f5 ("fscrypt: cache decrypted symlink target in ->i_link")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.