Flag close-on-exec can only be set on an allocated (but perhaps not yet installed) file descriptor. So if the bit in struct fdtable .open_fds array is not set, then value of matching bit in the .close_on_exec array is meaningless. This patch rely on this property to - remove initialization of unused part of .close_on_exec array; - remove clear of .close_on_exec bit when releasing a file descriptor. The patch takes care of adding the required check on .open_fds bit before looking for .close_on_exec bit. Link: http://lkml.kernel.org/r/1386796107-4197-1-git-send-email-ydroneaud@xxxxxxxxxx Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx> --- Hi Al and Mateusz, First of all, thank you for reviewing my previous patch and pointing out the error I've missed. Please consider this new patch which take the opposite approach: my previous patch assumed that .close_on_exec bit where defaulting to 0, but you prove this was a wrong assumption. This new patch assume that .close_on_exec bit are in a unknown, meaningless value when the file descriptor is not allocated. This way, there's no need to clear the value when releasing a file descriptor, and there's no need to initialize the .close_on_exec array. Unlike my previous patch, I haven't yet tested it. It's known to compile. Please try to find some corner cases I've missed in this other attempt. Regards. fs/file.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/fs/file.c b/fs/file.c index 4a78f981557a..3016e09d0290 100644 --- a/fs/file.c +++ b/fs/file.c @@ -78,7 +78,7 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) memcpy(nfdt->open_fds, ofdt->open_fds, cpy); memset((char *)(nfdt->open_fds) + cpy, 0, set); memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); - memset((char *)(nfdt->close_on_exec) + cpy, 0, set); + /* remaining portion of close_on_exec left uninitialized */ } static struct fdtable * alloc_fdtable(unsigned int nr) @@ -335,7 +335,7 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) int start = open_files / BITS_PER_LONG; memset(&new_fdt->open_fds[start], 0, left); - memset(&new_fdt->close_on_exec[start], 0, left); + /* remaining portion of close_on_exec left uninitialized */ } rcu_assign_pointer(newf->fdt, new_fdt); @@ -599,7 +599,6 @@ int __close_fd(struct files_struct *files, unsigned fd) if (!file) goto out_unlock; rcu_assign_pointer(fdt->fd[fd], NULL); - __clear_close_on_exec(fd, fdt); __put_unused_fd(files, fd); spin_unlock(&files->file_lock); return filp_close(file, files); @@ -622,10 +621,9 @@ void do_close_on_exec(struct files_struct *files) fdt = files_fdtable(files); if (fd >= fdt->max_fds) break; - set = fdt->close_on_exec[i]; + set = fdt->close_on_exec[i] & fdt->open_fds[i]; if (!set) continue; - fdt->close_on_exec[i] = 0; for ( ; set ; fd++, set >>= 1) { struct file *file; if (!(set & 1)) @@ -772,7 +770,7 @@ bool get_close_on_exec(unsigned int fd) bool res; rcu_read_lock(); fdt = files_fdtable(files); - res = close_on_exec(fd, fdt); + res = fd_is_open(fd, fdt) && close_on_exec(fd, fdt); rcu_read_unlock(); return res; } -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
