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Subject[PATCH] reiserfs: fix buffer overflow with long warning messages
Date
From: Eric Biggers <ebiggers@google.com>

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.

Reported-by: syzbot+b890b3335a4d8c608963@syzkaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/reiserfs/prints.c | 141 +++++++++++++++++++++++++------------------
1 file changed, 81 insertions(+), 60 deletions(-)

diff --git a/fs/reiserfs/prints.c b/fs/reiserfs/prints.c
index 7e288d97adcbb..9fed1c05f1f4d 100644
--- 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);

}
--
2.18.0
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