The patch titled seq_file: properly cope with pread has been removed from the -mm tree. Its filename was seq_file-properly-cope-with-pread.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: seq_file: properly cope with pread From: Eric Biederman <ebiederm@xxxxxxxxxxxx> Currently seq_read assumes that the offset passed to it is always the offset it passed to user space. In the case pread this assumption is broken and we do the wrong thing when presented with pread. To solve this I introduce an offset cache inside of struct seq_file so we know where our logical file position is. Then in seq_read if we try to read from another offset we reset our data structures and attempt to go to the offset user space wanted. [akpm@xxxxxxxxxxxxxxxxxxxx: restore FMODE_PWRITE] [pjt@xxxxxxxxxx: seq_open needs its fmode opened up to take advantage of this] Signed-off-by: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Paul Turner <pjt@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxx> [2.6.25.x, 2.6.26.x, 2.6.27.x, 2.6.28.x] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/seq_file.c | 36 ++++++++++++++++++++++++++++++++---- include/linux/seq_file.h | 1 + 2 files changed, 33 insertions(+), 4 deletions(-) diff -puN fs/seq_file.c~seq_file-properly-cope-with-pread fs/seq_file.c --- a/fs/seq_file.c~seq_file-properly-cope-with-pread +++ a/fs/seq_file.c @@ -48,8 +48,16 @@ int seq_open(struct file *file, const st */ file->f_version = 0; - /* SEQ files support lseek, but not pread/pwrite */ - file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE); + /* + * seq_files support lseek() and pread(). They do not implement + * write() at all, but we clear FMODE_PWRITE here for historical + * reasons. + * + * If a client of seq_files a) implements file.write() and b) wishes to + * support pwrite() then that client will need to implement its own + * file.open() which calls seq_open() and then sets FMODE_PWRITE. + */ + file->f_mode &= ~FMODE_PWRITE; return 0; } EXPORT_SYMBOL(seq_open); @@ -131,6 +139,22 @@ ssize_t seq_read(struct file *file, char int err = 0; mutex_lock(&m->lock); + + /* Don't assume *ppos is where we left it */ + if (unlikely(*ppos != m->read_pos)) { + m->read_pos = *ppos; + while ((err = traverse(m, *ppos)) == -EAGAIN) + ; + if (err) { + /* With prejudice... */ + m->read_pos = 0; + m->version = 0; + m->index = 0; + m->count = 0; + goto Done; + } + } + /* * seq_file->op->..m_start/m_stop/m_next may do special actions * or optimisations based on the file->f_version, so we want to @@ -230,8 +254,10 @@ Fill: Done: if (!copied) copied = err; - else + else { *ppos += copied; + m->read_pos += copied; + } file->f_version = m->version; mutex_unlock(&m->lock); return copied; @@ -266,16 +292,18 @@ loff_t seq_lseek(struct file *file, loff if (offset < 0) break; retval = offset; - if (offset != file->f_pos) { + if (offset != m->read_pos) { while ((retval=traverse(m, offset)) == -EAGAIN) ; if (retval) { /* with extreme prejudice... */ file->f_pos = 0; + m->read_pos = 0; m->version = 0; m->index = 0; m->count = 0; } else { + m->read_pos = offset; retval = file->f_pos = offset; } } diff -puN include/linux/seq_file.h~seq_file-properly-cope-with-pread include/linux/seq_file.h --- a/include/linux/seq_file.h~seq_file-properly-cope-with-pread +++ a/include/linux/seq_file.h @@ -19,6 +19,7 @@ struct seq_file { size_t from; size_t count; loff_t index; + loff_t read_pos; u64 version; struct mutex lock; const struct seq_operations *op; _ Patches currently in -mm which might be from ebiederm@xxxxxxxxxxxx are origin.patch linux-next.patch do_wait-fix-waiting-for-the-group-stop-with-the-dead-leader.patch reparent_thread-dont-call-kill_orphaned_pgrp-if-task_detached.patch reparent_thread-fix-the-is-it-traced-check.patch reparent_thread-fix-a-zombie-leak-if-sbin-init-ignores-sigchld.patch forget_original_parent-split-out-the-un-ptrace-part.patch forget_original_parent-do-not-abuse-child-ptrace_entry.patch forget_original_parent-do-not-abuse-child-ptrace_entry-fix.patch move-exit_ptrace-from-forget_original_parent-to-do_exit.patch reparent-untrace-do-nothing-if-no-childs-tracees.patch tracehook_notify_death-use-task_detached-helper.patch kthreads-simplify-the-startup-synchronization.patch kthreads-rework-kthread_stop.patch kthreads-simplify-migration_thread-exit-path.patch pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch kexec-add-dmesg-log-symbols-to-proc-vmcoreinfo-lists-fix-fix-fix.patch kexec-add-dmesg-log-symbols-to-proc-vmcoreinfo-lists-fix-fix-fix-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html