Since seq_read_iter looks mature enough to be used for /proc/<pid>/maps, re-allow applications to perform zero-copy data forwarding from it. Some executable-inspecting tools rely on patching entry point instructions with minimal machine code that uses sendfile to read /proc/self/maps to stdout. The sendfile call allows them to do it faster and without excessive allocations. This is inspired by the series by Cristoph Hellwig (linked). Changes since v1: only change proc_pid_maps_operations Link: https://lore.kernel.org/lkml/20201104082738.1054792-1-hch@xxxxxx/ Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops") Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Arkadiusz Kozdra (Arusekk) <arek_koz@xxxxx> --- fs/proc/task_mmu.c | 3 ++- fs/proc/task_nommu.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index e862cab69583..06282294ddb8 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -351,7 +351,8 @@ static int pid_maps_open(struct inode *inode, struct file *file) const struct file_operations proc_pid_maps_operations = { .open = pid_maps_open, - .read = seq_read, + .read_iter = seq_read_iter, + .splice_read = generic_file_splice_read, .llseek = seq_lseek, .release = proc_map_release, }; diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c index a6d21fc0033c..e55e79fd0175 100644 --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -295,7 +295,8 @@ static int pid_maps_open(struct inode *inode, struct file *file) const struct file_operations proc_pid_maps_operations = { .open = pid_maps_open, - .read = seq_read, + .read_iter = seq_read_iter, + .splice_read = generic_file_splice_read, .llseek = seq_lseek, .release = map_release, }; -- 2.31.1
