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...".
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@google.com ---
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 | 14 ++++++++++++-- fs/proc/fd.c | 4 ++++ 2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 779c05528e87..591f12d30d97 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -1886,14 +1886,16 @@ if precise results are needed. 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file --------------------------------------------------------------- This file provides information associated with an opened file. The regular -files have at least five fields -- 'pos', 'flags', 'mnt_id', 'ino', and 'size'. +files have at least six fields -- 'pos', 'flags', 'mnt_id', 'ino', 'size', +and 'path'.
The 'pos' represents the current offset of the opened file in decimal form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the file has been created with [see open(2) for details] and 'mnt_id' represents mount ID of the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo for details]. 'ino' represents the inode number of -the file, and 'size' represents the size of the file in bytes. +the file, 'size' represents the size of the file in bytes, and 'path' +represents the file path.
A typical output is::
@@ -1902,6 +1904,7 @@ A typical output is:: mnt_id: 19 ino: 63107 size: 0 + path: /dev/null
All locks associated with a file descriptor are shown in its fdinfo too::
@@ -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/proc/fd.c b/fs/proc/fd.c index 464bc3f55759..8889a8ba09d4 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -60,6 +60,10 @@ static int seq_show(struct seq_file *m, void *v) 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_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); if (seq_has_overflowed(m))