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proc: Track /proc/$pid/attr/ opener mm_struct
Commitbfb819ea20
("proc: Check /proc/$pid/attr/ writes against file opener") tried to make sure that there could not be a confusion between the opener of a /proc/$pid/attr/ file and the writer. It used struct cred to make sure the privileges didn't change. However, there were existing cases where a more privileged thread was passing the opened fd to a differently privileged thread (during container setup). Instead, use mm_struct to track whether the opener and writer are still the same process. (This is what several other proc files already do, though for different reasons.) Reported-by: Christian Brauner <christian.brauner@ubuntu.com> Reported-by: Andrea Righi <andrea.righi@canonical.com> Tested-by: Andrea Righi <andrea.righi@canonical.com> Fixes:bfb819ea20
("proc: Check /proc/$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>
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@ -2674,6 +2674,11 @@ out:
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}
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#ifdef CONFIG_SECURITY
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static int proc_pid_attr_open(struct inode *inode, struct file *file)
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{
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return __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS);
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}
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static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
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size_t count, loff_t *ppos)
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{
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@ -2704,7 +2709,7 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
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int rv;
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/* A task may only write when it was the opener. */
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if (file->f_cred != current_real_cred())
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if (file->private_data != current->mm)
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return -EPERM;
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rcu_read_lock();
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@ -2754,9 +2759,11 @@ out:
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}
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static const struct file_operations proc_pid_attr_operations = {
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.open = proc_pid_attr_open,
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.read = proc_pid_attr_read,
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.write = proc_pid_attr_write,
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.llseek = generic_file_llseek,
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.release = mem_release,
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};
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#define LSM_DIR_OPS(LSM) \
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