Messages in this thread Patch in this message | | | Date | Thu, 31 Aug 2017 21:12:51 +0200 | From | Michał Mirosław <> | Subject | [PATCH 2/2] procfs: let userspace find out max /proc/pid/comm length |
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Abuse llseek(SEEK_END) to return max /proc/pid/comm length.
This is needed for pthread_getname_np to be able to return ERANGE without modifying thread's name.
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> --- 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 7238a64751e4..48089f087a8e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1542,11 +1542,20 @@ 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, }; -- 2.11.0
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