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Message-Id: <20220623220613.3014268-3-kaleshsingh@google.com>
Date: Thu, 23 Jun 2022 15:06:07 -0700
From: Kalesh Singh <kaleshsingh@...gle.com>
To: ckoenig.leichtzumerken@...il.com, christian.koenig@....com,
viro@...iv.linux.org.uk, hch@...radead.org,
stephen.s.brennan@...cle.com, David.Laight@...LAB.COM
Cc: ilkos@...gle.com, tjmercier@...gle.com, surenb@...gle.com,
kernel-team@...roid.com, Kalesh Singh <kaleshsingh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Sumit Semwal <sumit.semwal@...aro.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>,
Christoph Anton Mitterer <mail@...istoph.anton.mitterer.name>,
Colin Cross <ccross@...gle.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Randy Dunlap <rdunlap@...radead.org>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: [PATCH v2 2/2] procfs: Add 'path' to /proc/<pid>/fdinfo/
In order to identify the type of memory a process has pinned through
its open fds, add the file path to fdinfo output. This allows
identifying memory types based on common prefixes:
e.g. "/memfd...", "/dmabuf...", "/dev/ashmem...".
To be cautious, only expose the paths for anonymous inodes, and this
also avoids printing path names with strange characters.
Access to /proc/<pid>/fdinfo is governed by PTRACE_MODE_READ_FSCREDS
the same as /proc/<pid>/maps which also exposes the file path of
mappings; so the security permissions for accessing path is consistent
with that of /proc/<pid>/maps.
Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
---
Changes in v2:
- Only add path field for files with anon inodes.
Changes from rfc:
- Split adding 'size' and 'path' into a separate patches, per Christian
- Fix indentation (use tabs) in documentaion, per Randy
Documentation/filesystems/proc.rst | 10 ++++++++++
fs/libfs.c | 9 +++++++++
fs/proc/fd.c | 13 +++++++++++--
include/linux/fs.h | 1 +
4 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 779c05528e87..ca23a9af4845 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -1907,6 +1907,9 @@ All locks associated with a file descriptor are shown in its fdinfo too::
lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
+Files with anonymous inodes have an additional 'path' field which represents
+the anonymous file path.
+
The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
pair provide additional information particular to the objects they represent.
@@ -1920,6 +1923,7 @@ Eventfd files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[eventfd]
eventfd-count: 5a
where 'eventfd-count' is hex value of a counter.
@@ -1934,6 +1938,7 @@ Signalfd files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[signalfd]
sigmask: 0000000000000200
where 'sigmask' is hex value of the signal mask associated
@@ -1949,6 +1954,7 @@ Epoll files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[eventpoll]
tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
where 'tfd' is a target file descriptor number in decimal form,
@@ -1968,6 +1974,7 @@ For inotify files the format is the following::
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:inotify
inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
where 'wd' is a watch descriptor in decimal form, i.e. a target file
@@ -1992,6 +1999,7 @@ For fanotify files the format is::
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[fanotify]
fanotify flags:10 event-flags:0
fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
@@ -2018,6 +2026,7 @@ Timerfd files
mnt_id: 9
ino: 63107
size: 0
+ path: anon_inode:[timerfd]
clockid: 0
ticks: 0
settime flags: 01
@@ -2042,6 +2051,7 @@ DMA Buffer files
mnt_id: 9
ino: 63107
size: 32768
+ path: /dmabuf:
count: 2
exp_name: system-heap
diff --git a/fs/libfs.c b/fs/libfs.c
index 31b0ddf01c31..6911749b4da7 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1217,6 +1217,15 @@ void kfree_link(void *p)
}
EXPORT_SYMBOL(kfree_link);
+static const struct address_space_operations anon_aops = {
+ .dirty_folio = noop_dirty_folio,
+};
+
+bool is_anon_inode(struct inode *inode)
+{
+ return inode->i_mapping->a_ops == &anon_aops;
+}
+
struct inode *alloc_anon_inode(struct super_block *s)
{
static const struct address_space_operations anon_aops = {
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 464bc3f55759..5bac79a2fa51 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -23,6 +23,7 @@ static int seq_show(struct seq_file *m, void *v)
struct files_struct *files = NULL;
int f_flags = 0, ret = -ENOENT;
struct file *file = NULL;
+ struct inode *inode = NULL;
struct task_struct *task;
task = get_proc_task(m->private);
@@ -54,11 +55,19 @@ static int seq_show(struct seq_file *m, void *v)
if (ret)
return ret;
+ inode = file_inode(file);
+
seq_printf(m, "pos:\t%lli\n", (long long)file->f_pos);
seq_printf(m, "flags:\t0%o\n", f_flags);
seq_printf(m, "mnt_id:\t%i\n", real_mount(file->f_path.mnt)->mnt_id);
- seq_printf(m, "ino:\t%lu\n", file_inode(file)->i_ino);
- seq_printf(m, "size:\t%lli\n", (long long)file_inode(file)->i_size);
+ seq_printf(m, "ino:\t%lu\n", inode->i_ino);
+ seq_printf(m, "size:\t%lli\n", (long long)inode->i_size);
+
+ if (is_anon_inode(inode)) {
+ seq_puts(m, "path:\t");
+ seq_file_path(m, file, "\n");
+ seq_putc(m, '\n');
+ }
/* show_fd_locks() never deferences files so a stale value is safe */
show_fd_locks(m, file, files);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9ad5e3520fae..73449e620b66 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3111,6 +3111,7 @@ extern void page_put_link(void *);
extern int page_symlink(struct inode *inode, const char *symname, int len);
extern const struct inode_operations page_symlink_inode_operations;
extern void kfree_link(void *);
+extern bool is_anon_inode(struct inode *inode);
void generic_fillattr(struct user_namespace *, struct inode *, struct kstat *);
void generic_fill_statx_attr(struct inode *inode, struct kstat *stat);
extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
--
2.37.0.rc0.161.g10f37bed90-goog
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