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ff7d80a9f2
We switch session state to SES_EXITING without cifs_tcp_ses_lock now,
it may lead to potential use-after-free issue.
Consider the following execution processes:
Thread 1:
__cifs_put_smb_ses()
spin_lock(&cifs_tcp_ses_lock)
if (--ses->ses_count > 0)
spin_unlock(&cifs_tcp_ses_lock)
return
spin_unlock(&cifs_tcp_ses_lock)
---> **GAP**
spin_lock(&ses->ses_lock)
if (ses->ses_status == SES_GOOD)
ses->ses_status = SES_EXITING
spin_unlock(&ses->ses_lock)
Thread 2:
cifs_find_smb_ses()
spin_lock(&cifs_tcp_ses_lock)
list_for_each_entry(ses, ...)
spin_lock(&ses->ses_lock)
if (ses->ses_status == SES_EXITING)
spin_unlock(&ses->ses_lock)
continue
...
spin_unlock(&ses->ses_lock)
if (ret)
cifs_smb_ses_inc_refcount(ret)
spin_unlock(&cifs_tcp_ses_lock)
If thread 1 is preempted in the gap and thread 2 start executing, thread 2
will get the session, and soon thread 1 will switch the session state to
SES_EXITING and start releasing it, even though thread 1 had increased the
session's refcount and still uses it.
So switch session state under cifs_tcp_ses_lock to eliminate this gap.
Signed-off-by: Winston Wen <wentao@uniontech.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
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.