reiserfs: fix buffer overflow with long warning messages

ReiserFS prepares log messages into a 1024-byte buffer with no bounds
checks.  Long messages, such as the "unknown mount option" warning when
userspace passes a crafted mount options string, overflow this buffer.
This causes KASAN to report a global-out-of-bounds write.

Fix it by truncating messages to the buffer size.

Link: http://lkml.kernel.org/r/20180707203621.30922-1-ebiggers3@gmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+b890b3335a4d8c608963@syzkaller.appspotmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/reiserfs/prints.c b/fs/reiserfs/prints.c
index 7e288d97adcbb7504f2c3c2953ca24debd770b01..9fed1c05f1f4df6f750c599da1670abf4b066445 100644 (file)
--- a/fs/reiserfs/prints.c
+++ b/fs/reiserfs/prints.c
@@ -76,83 +76,99 @@ static char *le_type(struct reiserfs_key *key)
 }
 
 /* %k */
-static void sprintf_le_key(char *buf, struct reiserfs_key *key)
+static int scnprintf_le_key(char *buf, size_t size, struct reiserfs_key *key)
 {
        if (key)
-               sprintf(buf, "[%d %d %s %s]", le32_to_cpu(key->k_dir_id),
-                       le32_to_cpu(key->k_objectid), le_offset(key),
-                       le_type(key));
+               return scnprintf(buf, size, "[%d %d %s %s]",
+                                le32_to_cpu(key->k_dir_id),
+                                le32_to_cpu(key->k_objectid), le_offset(key),
+                                le_type(key));
        else
-               sprintf(buf, "[NULL]");
+               return scnprintf(buf, size, "[NULL]");
 }
 
 /* %K */
-static void sprintf_cpu_key(char *buf, struct cpu_key *key)
+static int scnprintf_cpu_key(char *buf, size_t size, struct cpu_key *key)
 {
        if (key)
-               sprintf(buf, "[%d %d %s %s]", key->on_disk_key.k_dir_id,
-                       key->on_disk_key.k_objectid, reiserfs_cpu_offset(key),
-                       cpu_type(key));
+               return scnprintf(buf, size, "[%d %d %s %s]",
+                                key->on_disk_key.k_dir_id,
+                                key->on_disk_key.k_objectid,
+                                reiserfs_cpu_offset(key), cpu_type(key));
        else
-               sprintf(buf, "[NULL]");
+               return scnprintf(buf, size, "[NULL]");
 }
 
-static void sprintf_de_head(char *buf, struct reiserfs_de_head *deh)
+static int scnprintf_de_head(char *buf, size_t size,
+                            struct reiserfs_de_head *deh)
 {
        if (deh)
-               sprintf(buf,
-                       "[offset=%d dir_id=%d objectid=%d location=%d state=%04x]",
-                       deh_offset(deh), deh_dir_id(deh), deh_objectid(deh),
-                       deh_location(deh), deh_state(deh));
+               return scnprintf(buf, size,
+                                "[offset=%d dir_id=%d objectid=%d location=%d state=%04x]",
+                                deh_offset(deh), deh_dir_id(deh),
+                                deh_objectid(deh), deh_location(deh),
+                                deh_state(deh));
        else
-               sprintf(buf, "[NULL]");
+               return scnprintf(buf, size, "[NULL]");
 
 }
 
-static void sprintf_item_head(char *buf, struct item_head *ih)
+static int scnprintf_item_head(char *buf, size_t size, struct item_head *ih)
 {
        if (ih) {
-               strcpy(buf,
-                      (ih_version(ih) == KEY_FORMAT_3_6) ? "*3.6* " : "*3.5*");
-               sprintf_le_key(buf + strlen(buf), &(ih->ih_key));
-               sprintf(buf + strlen(buf), ", item_len %d, item_location %d, "
-                       "free_space(entry_count) %d",
-                       ih_item_len(ih), ih_location(ih), ih_free_space(ih));
+               char *p = buf;
+               char * const end = buf + size;
+
+               p += scnprintf(p, end - p, "%s",
+                              (ih_version(ih) == KEY_FORMAT_3_6) ?
+                              "*3.6* " : "*3.5*");
+
+               p += scnprintf_le_key(p, end - p, &ih->ih_key);
+
+               p += scnprintf(p, end - p,
+                              ", item_len %d, item_location %d, free_space(entry_count) %d",
+                              ih_item_len(ih), ih_location(ih),
+                              ih_free_space(ih));
+               return p - buf;
        } else
-               sprintf(buf, "[NULL]");
+               return scnprintf(buf, size, "[NULL]");
 }
 
-static void sprintf_direntry(char *buf, struct reiserfs_dir_entry *de)
+static int scnprintf_direntry(char *buf, size_t size,
+                             struct reiserfs_dir_entry *de)
 {
        char name[20];
 
        memcpy(name, de->de_name, de->de_namelen > 19 ? 19 : de->de_namelen);
        name[de->de_namelen > 19 ? 19 : de->de_namelen] = 0;
-       sprintf(buf, "\"%s\"==>[%d %d]", name, de->de_dir_id, de->de_objectid);
+       return scnprintf(buf, size, "\"%s\"==>[%d %d]",
+                        name, de->de_dir_id, de->de_objectid);
 }
 
-static void sprintf_block_head(char *buf, struct buffer_head *bh)
+static int scnprintf_block_head(char *buf, size_t size, struct buffer_head *bh)
 {
-       sprintf(buf, "level=%d, nr_items=%d, free_space=%d rdkey ",
-               B_LEVEL(bh), B_NR_ITEMS(bh), B_FREE_SPACE(bh));
+       return scnprintf(buf, size,
+                        "level=%d, nr_items=%d, free_space=%d rdkey ",
+                        B_LEVEL(bh), B_NR_ITEMS(bh), B_FREE_SPACE(bh));
 }
 
-static void sprintf_buffer_head(char *buf, struct buffer_head *bh)
+static int scnprintf_buffer_head(char *buf, size_t size, struct buffer_head *bh)
 {
-       sprintf(buf,
-               "dev %pg, size %zd, blocknr %llu, count %d, state 0x%lx, page %p, (%s, %s, %s)",
-               bh->b_bdev, bh->b_size,
-               (unsigned long long)bh->b_blocknr, atomic_read(&(bh->b_count)),
-               bh->b_state, bh->b_page,
-               buffer_uptodate(bh) ? "UPTODATE" : "!UPTODATE",
-               buffer_dirty(bh) ? "DIRTY" : "CLEAN",
-               buffer_locked(bh) ? "LOCKED" : "UNLOCKED");
+       return scnprintf(buf, size,
+                        "dev %pg, size %zd, blocknr %llu, count %d, state 0x%lx, page %p, (%s, %s, %s)",
+                        bh->b_bdev, bh->b_size,
+                        (unsigned long long)bh->b_blocknr,
+                        atomic_read(&(bh->b_count)),
+                        bh->b_state, bh->b_page,
+                        buffer_uptodate(bh) ? "UPTODATE" : "!UPTODATE",
+                        buffer_dirty(bh) ? "DIRTY" : "CLEAN",
+                        buffer_locked(bh) ? "LOCKED" : "UNLOCKED");
 }
 
-static void sprintf_disk_child(char *buf, struct disk_child *dc)
+static int scnprintf_disk_child(char *buf, size_t size, struct disk_child *dc)
 {
-       sprintf(buf, "[dc_number=%d, dc_size=%u]", dc_block_number(dc),
-               dc_size(dc));
+       return scnprintf(buf, size, "[dc_number=%d, dc_size=%u]",
+                        dc_block_number(dc), dc_size(dc));
 }
 
 static char *is_there_reiserfs_struct(char *fmt, int *what)
@@ -189,55 +205,60 @@ static void prepare_error_buf(const char *fmt, va_list args)
        char *fmt1 = fmt_buf;
        char *k;
        char *p = error_buf;
+       char * const end = &error_buf[sizeof(error_buf)];
        int what;
 
        spin_lock(&error_lock);
 
-       strcpy(fmt1, fmt);
+       if (WARN_ON(strscpy(fmt_buf, fmt, sizeof(fmt_buf)) < 0)) {
+               strscpy(error_buf, "format string too long", end - error_buf);
+               goto out_unlock;
+       }
 
        while ((k = is_there_reiserfs_struct(fmt1, &what)) != NULL) {
                *k = 0;
 
-               p += vsprintf(p, fmt1, args);
+               p += vscnprintf(p, end - p, fmt1, args);
 
                switch (what) {
                case 'k':
-                       sprintf_le_key(p, va_arg(args, struct reiserfs_key *));
+                       p += scnprintf_le_key(p, end - p,
+                                             va_arg(args, struct reiserfs_key *));
                        break;
                case 'K':
-                       sprintf_cpu_key(p, va_arg(args, struct cpu_key *));
+                       p += scnprintf_cpu_key(p, end - p,
+                                              va_arg(args, struct cpu_key *));
                        break;
                case 'h':
-                       sprintf_item_head(p, va_arg(args, struct item_head *));
+                       p += scnprintf_item_head(p, end - p,
+                                                va_arg(args, struct item_head *));
                        break;
                case 't':
-                       sprintf_direntry(p,
-                                        va_arg(args,
-                                               struct reiserfs_dir_entry *));
+                       p += scnprintf_direntry(p, end - p,
+                                               va_arg(args, struct reiserfs_dir_entry *));
                        break;
                case 'y':
-                       sprintf_disk_child(p,
-                                          va_arg(args, struct disk_child *));
+                       p += scnprintf_disk_child(p, end - p,
+                                                 va_arg(args, struct disk_child *));
                        break;
                case 'z':
-                       sprintf_block_head(p,
-                                          va_arg(args, struct buffer_head *));
+                       p += scnprintf_block_head(p, end - p,
+                                                 va_arg(args, struct buffer_head *));
                        break;
                case 'b':
-                       sprintf_buffer_head(p,
-                                           va_arg(args, struct buffer_head *));
+                       p += scnprintf_buffer_head(p, end - p,
+                                                  va_arg(args, struct buffer_head *));
                        break;
                case 'a':
-                       sprintf_de_head(p,
-                                       va_arg(args,
-                                              struct reiserfs_de_head *));
+                       p += scnprintf_de_head(p, end - p,
+                                              va_arg(args, struct reiserfs_de_head *));
                        break;
                }
 
-               p += strlen(p);
                fmt1 = k + 2;
        }
-       vsprintf(p, fmt1, args);
+       p += vscnprintf(p, end - p, fmt1, args);
+out_unlock:
        spin_unlock(&error_lock);
 
 }