path: root/fs
diff options
authorKees Cook <>2021-06-08 10:12:21 -0700
committerLinus Torvalds <>2021-06-08 10:24:09 -0700
commit591a22c14d3f45cc38bd1931c593c221df2f1881 (patch)
treea401c5309eec40ab5304390474e923871e96c509 /fs
parent4c8684fe555e95100030bd330d0a2780ac27952e (diff)
proc: Track /proc/$pid/attr/ opener mm_struct
Commit bfb819ea20ce ("proc: Check /proc/$pid/attr/ writes against file opener") tried to make sure that there could not be a confusion between the opener of a /proc/$pid/attr/ file and the writer. It used struct cred to make sure the privileges didn't change. However, there were existing cases where a more privileged thread was passing the opened fd to a differently privileged thread (during container setup). Instead, use mm_struct to track whether the opener and writer are still the same process. (This is what several other proc files already do, though for different reasons.) Reported-by: Christian Brauner <> Reported-by: Andrea Righi <> Tested-by: Andrea Righi <> Fixes: bfb819ea20ce ("proc: Check /proc/$pid/attr/ writes against file opener") Cc: Signed-off-by: Kees Cook <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'fs')
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 58bbf334265b..7118ebe38fa6 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2674,6 +2674,11 @@ out:
+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)
@@ -2704,7 +2709,7 @@ 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;
@@ -2754,9 +2759,11 @@ out:
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) \