name : stream_open.cocci // SPDX-License-Identifier: GPL-2.0 // Author: Kirill Smelkov (kirr@nexedi.com) // // Search for stream-like files that are using nonseekable_open and convert // them to stream_open. A stream-like file is a file that does not use ppos in // its read and write. Rationale for the conversion is to avoid deadlock in // between read and write. virtual report virtual patch virtual explain // explain decisions in the patch (SPFLAGS="-D explain") // stream-like reader & writer - ones that do not depend on f_pos. @ stream_reader @ identifier readstream, ppos; identifier f, buf, len; type loff_t; @@ ssize_t readstream(struct file *f, char *buf, size_t len, loff_t *ppos) { ... when != ppos } @ stream_writer @ identifier writestream, ppos; identifier f, buf, len; type loff_t; @@ ssize_t writestream(struct file *f, const char *buf, size_t len, loff_t *ppos) { ... when != ppos } // a function that blocks @ blocks @ identifier block_f; identifier wait =~ "^wait_.*"; @@ block_f(...) { ... when exists wait(...) ... when exists } // stream_reader that can block inside. // // XXX wait_* can be called not directly from current function (e.g. func -> f -> g -> wait()) // XXX currently reader_blocks supports only direct and 1-level indirect cases. @ reader_blocks_direct @ identifier stream_reader.readstream; identifier wait =~ "^wait_.*"; @@ readstream(...) { ... when exists wait(...) ... when exists } @ reader_blocks_1 @ identifier stream_reader.readstream; identifier blocks.block_f; @@ readstream(...) { ... when exists block_f(...) ... when exists } @ reader_blocks depends on reader_blocks_direct || reader_blocks_1 @ identifier stream_reader.readstream; @@ readstream(...) { ... } // file_operations + whether they have _any_ .read, .write, .llseek ... at all. // // XXX add support for file_operations xxx[N] = ... (sound/core/pcm_native.c) @ fops0 @ identifier fops; @@ struct file_operations fops = { ... }; @ has_read @ identifier fops0.fops; identifier read_f; @@ struct file_operations fops = { .read = read_f, }; @ has_read_iter @ identifier fops0.fops; identifier read_iter_f; @@ struct file_operations fops = { .read_iter = read_iter_f, }; @ has_write @ identifier fops0.fops; identifier write_f; @@ struct file_operations fops = { .write = write_f, }; @ has_write_iter @ identifier fops0.fops; identifier write_iter_f; @@ struct file_operations fops = { .write_iter = write_iter_f, }; @ has_llseek @ identifier fops0.fops; identifier llseek_f; @@ struct file_operations fops = { .llseek = llseek_f, }; @ has_no_llseek @ identifier fops0.fops; @@ struct file_operations fops = { .llseek = no_llseek, }; @ has_noop_llseek @ identifier fops0.fops; @@ struct file_operations fops = { .llseek = noop_llseek, }; @ has_mmap @ identifier fops0.fops; identifier mmap_f; @@ struct file_operations fops = { .mmap = mmap_f, }; @ has_copy_file_range @ identifier fops0.fops; identifier copy_file_range_f; @@ struct file_operations fops = { .copy_file_range = copy_file_range_f, }; @ has_remap_file_range @ identifier fops0.fops; identifier remap_file_range_f; @@ struct file_operations fops = { .remap_file_range = remap_file_range_f, }; @ has_splice_read @ identifier fops0.fops; identifier splice_read_f; @@ struct file_operations fops = { .splice_read = splice_read_f, }; @ has_splice_write @ identifier fops0.fops; identifier splice_write_f; @@ struct file_operations fops = { .splice_write = splice_write_f, }; // file_operations that is candidate for stream_open conversion - it does not // use mmap and other methods that assume @offset access to file. // // XXX for simplicity require no .{read/write}_iter and no .splice_{read/write} for now. // XXX maybe_steam.fops cannot be used in other rules - it gives "bad rule maybe_stream or bad variable fops". @ maybe_stream depends on (!has_llseek || has_no_llseek || has_noop_llseek) && !has_mmap && !has_copy_file_range && !has_remap_file_range && !has_read_iter && !has_write_iter && !has_splice_read && !has_splice_write @ identifier fops0.fops; @@ struct file_operations fops = { }; // ---- conversions ---- // XXX .open = nonseekable_open -> .open = stream_open // XXX .open = func -> openfunc -> nonseekable_open // read & write // // if both are used in the same file_operations together with an opener - // under that conditions we can use stream_open instead of nonseekable_open. @ fops_rw depends on maybe_stream @ identifier fops0.fops, openfunc; identifier stream_reader.readstream; identifier stream_writer.writestream; @@ struct file_operations fops = { .open = openfunc, .read = readstream, .write = writestream, }; @ report_rw depends on report @ identifier fops_rw.openfunc; position p1; @@ openfunc(...) { <... nonseekable_open@p1 ...> } @ script:python depends on report && reader_blocks @ fops << fops0.fops; p << report_rw.p1; @@ coccilib.report.print_report(p[0], "ERROR: %s: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix." % (fops,)) @ script:python depends on report && !reader_blocks @ fops << fops0.fops; p << report_rw.p1; @@ coccilib.report.print_report(p[0], "WARNING: %s: .read() and .write() have stream semantic; safe to change nonseekable_open -> stream_open." % (fops,)) @ explain_rw_deadlocked depends on explain && reader_blocks @ identifier fops_rw.openfunc; @@ openfunc(...) { <... - nonseekable_open + nonseekable_open /* read & write (was deadlock) */ ...> } @ explain_rw_nodeadlock depends on explain && !reader_blocks @ identifier fops_rw.openfunc; @@ openfunc(...) { <... - nonseekable_open + nonseekable_open /* read & write (no direct deadlock) */ ...> } @ patch_rw depends on patch @ identifier fops_rw.openfunc; @@ openfunc(...) { <... - nonseekable_open + stream_open ...> } // read, but not write @ fops_r depends on maybe_stream && !has_write @ identifier fops0.fops, openfunc; identifier stream_reader.readstream; @@ struct file_operations fops = { .open = openfunc, .read = readstream, }; @ report_r depends on report @ identifier fops_r.openfunc; position p1; @@ openfunc(...) { <... nonseekable_open@p1 ...> } @ script:python depends on report @ fops << fops0.fops; p << report_r.p1; @@ coccilib.report.print_report(p[0], "WARNING: %s: .read() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,)) @ explain_r depends on explain @ identifier fops_r.openfunc; @@ openfunc(...) { <... - nonseekable_open + nonseekable_open /* read only */ ...> } @ patch_r depends on patch @ identifier fops_r.openfunc; @@ openfunc(...) { <... - nonseekable_open + stream_open ...> } // write, but not read @ fops_w depends on maybe_stream && !has_read @ identifier fops0.fops, openfunc; identifier stream_writer.writestream; @@ struct file_operations fops = { .open = openfunc, .write = writestream, }; @ report_w depends on report @ identifier fops_w.openfunc; position p1; @@ openfunc(...) { <... nonseekable_open@p1 ...> } @ script:python depends on report @ fops << fops0.fops; p << report_w.p1; @@ coccilib.report.print_report(p[0], "WARNING: %s: .write() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,)) @ explain_w depends on explain @ identifier fops_w.openfunc; @@ openfunc(...) { <... - nonseekable_open + nonseekable_open /* write only */ ...> } @ patch_w depends on patch @ identifier fops_w.openfunc; @@ openfunc(...) { <... - nonseekable_open + stream_open ...> } // no read, no write - don't change anything