Implement lseek(fd, 0, SEEK_END) for /proc/PID/comm to return max
task name length.
This will allow eg. pthread_getname_np() to be able to return ERANGE
without modifying thread's name.
Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
---
fs/proc/base.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3a3b566443e5..80f5911f2ea9 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1575,11 +1575,20 @@ static int comm_open(struct inode *inode, struct file *filp)
return single_open(filp, comm_show, inode);
}
+static loff_t comm_lseek(struct file *file, loff_t offset, int whence)
+{
+ /* SEEK_END for seq_files normally gets -EINVAL */
+ if (whence == SEEK_END && offset == 0)
+ return TASK_COMM_LEN - 1;
+
+ return seq_lseek(file, offset, whence);
+}
+
static const struct file_operations proc_pid_set_comm_operations = {
.open = comm_open,
.read = seq_read,
.write = comm_write,
- .llseek = seq_lseek,
+ .llseek = comm_lseek,
.release = single_release,
};
--
2.19.2
