Brad Bishop | c342db3 | 2019-05-15 21:57:59 -0400 | [diff] [blame] | 1 | From 547c3710a1493d2fd6bb56b819cf162db433756a Mon Sep 17 00:00:00 2001 |
| 2 | From: Richard Purdie <richard.purdie@linuxfoundation.org> |
| 3 | Date: Wed, 9 Mar 2016 22:49:02 +0000 |
| 4 | Subject: [PATCH] qemu: Limit paths searched during user mode emulation |
| 5 | |
| 6 | By default qemu builds a complete list of directories within the user |
| 7 | emulation sysroot (-L option). The OE sysroot directory is large and |
| 8 | this is confusing, for example it indexes all pkgdata. In particular this |
| 9 | confuses strace of qemu binaries with tons of irrelevant paths. |
| 10 | |
| 11 | This patch stops the code indexing up front and instead only indexes |
| 12 | things if/as/when it needs to. This drastically reduces the files it |
| 13 | reads and reduces memory usage and cleans up strace. |
| 14 | |
| 15 | It would also avoid the infinite directory traversal bug in [YOCTO #6996] |
| 16 | although the code could still be vulnerable if it parsed those specific |
| 17 | paths. |
| 18 | |
| 19 | RP |
| 20 | 2016/3/9 |
| 21 | Upstream-Status: Pending |
| 22 | |
| 23 | --- |
| 24 | util/path.c | 44 ++++++++++++++++++++++---------------------- |
| 25 | 1 file changed, 22 insertions(+), 22 deletions(-) |
| 26 | |
| 27 | diff --git a/util/path.c b/util/path.c |
| 28 | index 7f9fc272..a416cd4a 100644 |
| 29 | --- a/util/path.c |
| 30 | +++ b/util/path.c |
| 31 | @@ -15,6 +15,7 @@ struct pathelem |
| 32 | char *name; |
| 33 | /* Full path name, eg. /usr/gnemul/x86-linux/lib. */ |
| 34 | char *pathname; |
| 35 | + int populated_entries; |
| 36 | struct pathelem *parent; |
| 37 | /* Children */ |
| 38 | unsigned int num_entries; |
| 39 | @@ -45,6 +46,7 @@ static struct pathelem *new_entry(const char *root, |
| 40 | new->name = g_strdup(name); |
| 41 | new->pathname = g_strdup_printf("%s/%s", root, name); |
| 42 | new->num_entries = 0; |
| 43 | + new->populated_entries = 0; |
| 44 | return new; |
| 45 | } |
| 46 | |
| 47 | @@ -53,15 +55,16 @@ static struct pathelem *new_entry(const char *root, |
| 48 | /* Not all systems provide this feature */ |
| 49 | #if defined(DT_DIR) && defined(DT_UNKNOWN) && defined(DT_LNK) |
| 50 | # define dirent_type(dirent) ((dirent)->d_type) |
| 51 | -# define is_dir_maybe(type) \ |
| 52 | - ((type) == DT_DIR || (type) == DT_UNKNOWN || (type) == DT_LNK) |
| 53 | +# define is_not_dir(type) \ |
| 54 | + ((type) != DT_DIR && (type) != DT_UNKNOWN && (type) != DT_LNK) |
| 55 | #else |
| 56 | # define dirent_type(dirent) (1) |
| 57 | -# define is_dir_maybe(type) (type) |
| 58 | +# define is_not_dir(type) (0) |
| 59 | #endif |
| 60 | |
| 61 | static struct pathelem *add_dir_maybe(struct pathelem *path) |
| 62 | { |
| 63 | + unsigned int i; |
| 64 | DIR *dir; |
| 65 | |
| 66 | if ((dir = opendir(path->pathname)) != NULL) { |
| 67 | @@ -74,6 +77,11 @@ static struct pathelem *add_dir_maybe(struct pathelem *path) |
| 68 | } |
| 69 | closedir(dir); |
| 70 | } |
| 71 | + |
| 72 | + for (i = 0; i < path->num_entries; i++) |
| 73 | + (path->entries[i])->parent = path; |
| 74 | + |
| 75 | + path->populated_entries = 1; |
| 76 | return path; |
| 77 | } |
| 78 | |
| 79 | @@ -89,26 +97,16 @@ static struct pathelem *add_entry(struct pathelem *root, const char *name, |
| 80 | e = &root->entries[root->num_entries-1]; |
| 81 | |
| 82 | *e = new_entry(root->pathname, root, name); |
| 83 | - if (is_dir_maybe(type)) { |
| 84 | - *e = add_dir_maybe(*e); |
| 85 | + if (is_not_dir(type)) { |
| 86 | + (*e)->populated_entries = 1; |
| 87 | } |
| 88 | |
| 89 | return root; |
| 90 | } |
| 91 | |
| 92 | -/* This needs to be done after tree is stabilized (ie. no more reallocs!). */ |
| 93 | -static void set_parents(struct pathelem *child, struct pathelem *parent) |
| 94 | -{ |
| 95 | - unsigned int i; |
| 96 | - |
| 97 | - child->parent = parent; |
| 98 | - for (i = 0; i < child->num_entries; i++) |
| 99 | - set_parents(child->entries[i], child); |
| 100 | -} |
| 101 | - |
| 102 | /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */ |
| 103 | static const char * |
| 104 | -follow_path(const struct pathelem *cursor, const char *name) |
| 105 | +follow_path(struct pathelem *cursor, struct pathelem **source, const char *name) |
| 106 | { |
| 107 | unsigned int i, namelen; |
| 108 | |
| 109 | @@ -119,14 +117,18 @@ follow_path(const struct pathelem *cursor, const char *name) |
| 110 | return cursor->pathname; |
| 111 | |
| 112 | if (strneq(name, namelen, "..")) |
| 113 | - return follow_path(cursor->parent, name + namelen); |
| 114 | + return follow_path(cursor->parent, &cursor->parent, name + namelen); |
| 115 | |
| 116 | if (strneq(name, namelen, ".")) |
| 117 | - return follow_path(cursor, name + namelen); |
| 118 | + return follow_path(cursor, source, name + namelen); |
| 119 | + |
| 120 | + if (!cursor->populated_entries) |
| 121 | + *source = add_dir_maybe(cursor); |
| 122 | + cursor = *source; |
| 123 | |
| 124 | for (i = 0; i < cursor->num_entries; i++) |
| 125 | if (strneq(name, namelen, cursor->entries[i]->name)) |
| 126 | - return follow_path(cursor->entries[i], name + namelen); |
| 127 | + return follow_path(cursor->entries[i], &cursor->entries[i], name + namelen); |
| 128 | |
| 129 | /* Not found */ |
| 130 | return NULL; |
| 131 | @@ -160,8 +162,6 @@ void init_paths(const char *prefix) |
| 132 | g_free(base->name); |
| 133 | g_free(base); |
| 134 | base = NULL; |
| 135 | - } else { |
| 136 | - set_parents(base, base); |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | @@ -173,5 +173,5 @@ const char *path(const char *name) |
| 141 | if (!base || !name || name[0] != '/') |
| 142 | return name; |
| 143 | |
| 144 | - return follow_path(base, name) ?: name; |
| 145 | + return follow_path(base, &base, name) ?: name; |
| 146 | } |