From: Kees Cook <keescook@chromium.org> stable inclusion from stable-v5.10.44 commit f70102cb369cde6ab7551ca58152d00fd3478fec bugzilla: CVE: NA -------------------------------- commit 591a22c14d3f45cc38bd1931c593c221df2f1881 upstream. Commit bfb819ea20ce ("proc: Check /proc/$pid/attr/ writes against file opener") tried to make sure that there could not be a confusion between the opener of a /proc/$pid/attr/ file and the writer. It used struct cred to make sure the privileges didn't change. However, there were existing cases where a more privileged thread was passing the opened fd to a differently privileged thread (during container setup). Instead, use mm_struct to track whether the opener and writer are still the same process. (This is what several other proc files already do, though for different reasons.) Reported-by: Christian Brauner <christian.brauner@ubuntu.com> Reported-by: Andrea Righi <andrea.righi@canonical.com> Tested-by: Andrea Righi <andrea.righi@canonical.com> Fixes: bfb819ea20ce ("proc: Check /proc/$pid/attr/ writes against file opener") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: bobo~ <931671772@qq.com> --- fs/proc/base.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 720e2e524cb1..a2d472b0c2e3 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2691,6 +2691,11 @@ static int proc_pident_readdir(struct file *file, struct dir_context *ctx, } #ifdef CONFIG_SECURITY +static int proc_pid_attr_open(struct inode *inode, struct file *file) +{ + return __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS); +} + static ssize_t proc_pid_attr_read(struct file * file, char __user * buf, size_t count, loff_t *ppos) { @@ -2721,7 +2726,7 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf, int rv; /* A task may only write when it was the opener. */ - if (file->f_cred != current_real_cred()) + if (file->private_data != current->mm) return -EPERM; rcu_read_lock(); @@ -2771,9 +2776,11 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf, } static const struct file_operations proc_pid_attr_operations = { + .open = proc_pid_attr_open, .read = proc_pid_attr_read, .write = proc_pid_attr_write, .llseek = generic_file_llseek, + .release = mem_release, }; #define LSM_DIR_OPS(LSM) \ -- 2.23.0