The patch titled
Subject: procfs: prevent unprivileged processes accessing fdinfo
has been added to the -mm tree. Its filename is
procfs-prevent-unpriveleged-processes-accessing-fdinfo.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/procfs-prevent-unpriveleged-processes-accessing-fdinfo.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/procfs-prevent-unpriveleged-processes-accessing-fdinfo.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Subject: procfs: prevent unprivileged processes accessing fdinfo
The file permissions on the fdinfo dir from were changed from
S_IRUSR|S_IXUSR to S_IRUGO|S_IXUGO, and a PTRACE_MODE_READ check was added
for opening the fdinfo files [1]. However, the ptrace permission check
was not added to the directory, allowing anyone to get the open FD numbers
by reading the fdinfo directory.
Add the missing ptrace permission check for opening the fdinfo directory.
The check is also added for readdir, lseek in the case that an
unprivileged process inherits an open FD to the fdinfo dir after an exec.
For the same reason, similar checks are added for fdinfo files which
previously only checked the ptrace permission in open.
[1] https://lkml.kernel.org/r/20210308170651.919148-1-kaleshsingh@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210708155647.44208-1-kaleshsingh@xxxxxxxxxx
Fixes: 7bc3fa0172a4 ("procfs: allow reading fdinfo with PTRACE_MODE_READ")
Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/fd.c | 65 +++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 61 insertions(+), 4 deletions(-)
--- a/fs/proc/fd.c~procfs-prevent-unpriveleged-processes-accessing-fdinfo
+++ a/fs/proc/fd.c
@@ -72,7 +72,7 @@ out:
return 0;
}
-static int seq_fdinfo_open(struct inode *inode, struct file *file)
+static int proc_fdinfo_access_allowed(struct inode *inode)
{
bool allowed = false;
struct task_struct *task = get_proc_task(inode);
@@ -86,13 +86,44 @@ static int seq_fdinfo_open(struct inode
if (!allowed)
return -EACCES;
+ return 0;
+}
+
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
+{
+ int ret = proc_fdinfo_access_allowed(inode);
+
+ if (ret)
+ return ret;
+
return single_open(file, seq_show, inode);
}
+static ssize_t seq_fdinfo_read(struct file *file, char __user *buf, size_t size,
+ loff_t *ppos)
+{
+ int ret = proc_fdinfo_access_allowed(file_inode(file));
+
+ if (ret)
+ return ret;
+
+ return seq_read(file, buf, size, ppos);
+}
+
+static loff_t seq_fdinfo_lseek(struct file *file, loff_t offset, int whence)
+{
+ int ret = proc_fdinfo_access_allowed(file_inode(file));
+
+ if (ret)
+ return ret;
+
+ return seq_lseek(file, offset, whence);
+}
+
static const struct file_operations proc_fdinfo_file_operations = {
.open = seq_fdinfo_open,
- .read = seq_read,
- .llseek = seq_lseek,
+ .read = seq_fdinfo_read,
+ .llseek = seq_fdinfo_lseek,
.release = single_release,
};
@@ -344,17 +375,43 @@ proc_lookupfdinfo(struct inode *dir, str
static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
{
+ int ret = proc_fdinfo_access_allowed(file_inode(file));
+
+ if (ret)
+ return ret;
+
return proc_readfd_common(file, ctx,
proc_fdinfo_instantiate);
}
+static loff_t proc_llseek_fdinfo(struct file *file, loff_t offset, int whence)
+{
+ int ret = proc_fdinfo_access_allowed(file_inode(file));
+
+ if (ret)
+ return ret;
+
+ return generic_file_llseek(file, offset, whence);
+}
+
+static int proc_open_fdinfo(struct inode *inode, struct file *file)
+{
+ int ret = proc_fdinfo_access_allowed(inode);
+
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
const struct inode_operations proc_fdinfo_inode_operations = {
.lookup = proc_lookupfdinfo,
.setattr = proc_setattr,
};
const struct file_operations proc_fdinfo_operations = {
+ .open = proc_open_fdinfo,
.read = generic_read_dir,
.iterate_shared = proc_readfdinfo,
- .llseek = generic_file_llseek,
+ .llseek = proc_llseek_fdinfo,
};
_
Patches currently in -mm which might be from kaleshsingh@xxxxxxxxxx are
procfs-prevent-unpriveleged-processes-accessing-fdinfo.patch
