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Dawson Engler writes:
> enclosed are 84 potential errors where code
> (1) checks if a pointer is null
> (2) dereferences it anyway.
> ---------------------------------------------------------
> [BUG] seems like it. it's not guarded. or is there some weird dependence?
> /u2/engler/mc/oses/linux/2.4.4-ac8/fs/ext2/dir.c:61:ext2_check_dir_entry: ERROR:INTERNAL_NULL:53:61: [type=set] (set at line 53) Dereferencing NULL ptr "dir" illegally!
> ---------------------------------------------------------
> [BUG] [GEM] another blow up because of error printouts
> /u2/engler/mc/oses/linux/2.4.4-ac8/fs/hpfs/dir.c:215:hpfs_lookup: ERROR:INTERNAL_NULL:213:215: [type=set] (set at line 213) Dereferencing NULL ptr "result" illegally!
> ---------------------------------------------------------
> [BUG] seems to blow up with malformed input.
> /u2/engler/mc/oses/linux/2.4.4-ac8/fs/hpfs/super.c:215:parse_opts: ERROR:INTERNAL_NULL:180:215: [type=null] (set at line 180) WARN: Passing NULL pointer "rhs" as arg 0 to function strcmp
> ---------------------------------------------------------
> [BUG] seems identical to the ext2 one.
> /u2/engler/mc/oses/linux/2.4.4-ac8/fs/ufs/dir.c:178:ufs_check_dir_entry: ERROR:INTERNAL_NULL:170:178: [type=set] (set at line 170) Dereferencing NULL ptr "dir" illegally!
> ---------------------------------------------------------
> [BUG] looks bad.
> /u2/engler/mc/oses/linux/2.4.4-ac8/fs/ufs/super.c:271:ufs_parse_options: ERROR:INTERNAL_NULL:267:271: [type=null] (set at line 267) WARN: Passing NULL pointer "value" as arg 0 to function strcmp

OK, attached is a patch which fixes the above checker bugs under fs/.

For ufs/dir.c it was overzealous verification (and or copying from ext2) -
dir could not be NULL (the supplied pointer is dereferenced in each of
the calling functions before ufs_check_dir_entry() is called).

For ext2 it is pretty much the same, except ext2_delete_entry() called
ext2_check_dir_entry() with a NULL input (for some reason), but it could
easily supply a valid input value. All callers to ext2_delete_entry()
dereference the dir parameter before calling ext2_delete_entry(). All
other paths dereference dir before ext2_check_dir_entry() is called.

UFS and HPFS maintainers CC'd in case they want to object, but it is
pretty straight forward stuff.

Cheers, Andreas
===========================================================================
diff -ru linux-2.4.5.orig/fs/ext2/dir.c linux-2.4.5-aed/fs/ext2/dir.c
--- linux-2.4.5.orig/fs/ext2/dir.c Fri Dec 8 18:35:54 2000
+++ linux-2.4.5-aed/fs/ext2/dir.c Tue May 29 19:42:02 2001
@@ -40,17 +43,18 @@
unsigned long offset)
{
const char * error_msg = NULL;
+ int rlen = le16_to_cpu(de->rec_len);

- if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(1))
+ if (rlen < EXT2_DIR_REC_LEN(1))
error_msg = "rec_len is smaller than minimal";
- else if (le16_to_cpu(de->rec_len) % 4 != 0)
+ else if (rlen % 4 != 0)
error_msg = "rec_len % 4 != 0";
- else if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(de->name_len))
+ else if (rlen < EXT2_DIR_REC_LEN(de->name_len))
error_msg = "rec_len is too small for name_len";
- else if (dir && ((char *) de - bh->b_data) + le16_to_cpu(de->rec_len) >
- dir->i_sb->s_blocksize)
+ else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
error_msg = "directory entry across blocks";
- else if (dir && le32_to_cpu(de->inode) > le32_to_cpu(dir->i_sb->u.ext2_sb.s_es->s_inodes_count))
+ else if (le32_to_cpu(de->inode) >
+ le32_to_cpu(dir->i_sb->u.ext2_sb.s_es->s_inodes_count))
error_msg = "inode out of bounds";

if (error_msg != NULL)
@@ -58,7 +62,7 @@
"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
dir->i_ino, error_msg, offset,
(unsigned long) le32_to_cpu(de->inode),
- le16_to_cpu(de->rec_len), de->name_len);
+ rlen, de->name_len);
return error_msg == NULL ? 1 : 0;
}

diff -ru linux-2.4.5.orig/fs/ext2/namei.c linux-2.4.5-aed/fs/ext2/namei.c
--- linux-2.4.5.orig/fs/ext2/namei.c Tue Apr 10 16:43:25 2001
+++ linux-2.4.5-aed/fs/ext2/namei.c Tue May 29 19:40:10 2001
@@ -327,8 +327,7 @@
pde = NULL;
de = (struct ext2_dir_entry_2 *) bh->b_data;
while (i < bh->b_size) {
- if (!ext2_check_dir_entry ("ext2_delete_entry", NULL,
- de, bh, i))
+ if (!ext2_check_dir_entry("ext2_delete_entry", dir, de, bh, i))
return -EIO;
if (de == de_del) {
if (pde)
diff -ru linux-2.4.5.orig/fs/hpfs/dir.c linux-2.4.5-aed/fs/hpfs/dir.c
--- linux-2.4.5.orig/fs/hpfs/dir.c Fri Aug 11 15:29:01 2000
+++ linux-2.4.5-aed/fs/hpfs/dir.c Tue May 29 19:32:57 2001
@@ -212,7 +212,7 @@
hpfs_lock_iget(dir->i_sb, de->directory || (de->ea_size && dir->i_sb->s_hpfs_eas) ? 1 : 2);
if (!(result = iget(dir->i_sb, ino))) {
hpfs_unlock_iget(dir->i_sb);
- hpfs_error(result->i_sb, "hpfs_lookup: can't get inode");
+ hpfs_error(dir->i_sb, "hpfs_lookup: can't get inode");
goto bail1;
}
if (!de->directory) result->i_hpfs_parent_dir = dir->i_ino;
diff -ru linux-2.4.5.orig/fs/hpfs/super.c linux-2.4.5-aed/fs/hpfs/super.c
--- linux-2.4.5.orig/fs/hpfs/super.c Tue May 8 17:17:20 2001
+++ linux-2.4.5-aed/fs/hpfs/super.c Tue May 29 20:16:22 2001
@@ -212,6 +212,8 @@
return 0;
}
else if (!strcmp(p, "case")) {
+ if (!rhs || !*rhs)
+ return 0;
if (!strcmp(rhs, "lower"))
*lowercase = 1;
else if (!strcmp(rhs, "asis"))
@@ -220,6 +222,8 @@
return 0;
}
else if (!strcmp(p, "conv")) {
+ if (!rhs || !*rhs)
+ return 0;
if (!strcmp(rhs, "binary"))
*conv = CONV_BINARY;
else if (!strcmp(rhs, "text"))
@@ -230,6 +234,8 @@
return 0;
}
else if (!strcmp(p, "check")) {
+ if (!rhs || !*rhs)
+ return 0;
if (!strcmp(rhs, "none"))
*chk = 0;
else if (!strcmp(rhs, "normal"))
@@ -240,6 +246,8 @@
return 0;
}
else if (!strcmp(p, "errors")) {
+ if (!rhs || !*rhs)
+ return 0;
if (!strcmp(rhs, "continue"))
*errs = 0;
else if (!strcmp(rhs, "remount-ro"))
@@ -250,6 +258,8 @@
return 0;
}
else if (!strcmp(p, "eas")) {
+ if (!rhs || !*rhs)
+ return 0;
if (!strcmp(rhs, "no"))
*eas = 0;
else if (!strcmp(rhs, "ro"))
@@ -260,6 +270,8 @@
return 0;
}
else if (!strcmp(p, "chkdsk")) {
+ if (!rhs || !*rhs)
+ return 0;
if (!strcmp(rhs, "no"))
*chkdsk = 0;
else if (!strcmp(rhs, "errors"))
diff -ru linux-2.4.5.orig/fs/ufs/dir.c linux-2.4.5-aed/fs/ufs/dir.c
--- linux-2.4.5.orig/fs/ufs/dir.c Fri Aug 11 15:29:02 2000
+++ linux-2.4.5-aed/fs/ufs/dir.c Tue May 29 20:10:35 2001
@@ -152,22 +152,23 @@
struct super_block * sb;
const char * error_msg;
unsigned flags, swab;
-
+ int rlen = SWAB16(de->d_reclen);
+
sb = dir->i_sb;
flags = sb->u.ufs_sb.s_flags;
swab = sb->u.ufs_sb.s_swab;
error_msg = NULL;
-
- if (SWAB16(de->d_reclen) < UFS_DIR_REC_LEN(1))
+
+ if (rlen < UFS_DIR_REC_LEN(1))
error_msg = "reclen is smaller than minimal";
- else if (SWAB16(de->d_reclen) % 4 != 0)
+ else if (rlen % 4 != 0)
error_msg = "reclen % 4 != 0";
- else if (SWAB16(de->d_reclen) < UFS_DIR_REC_LEN(ufs_get_de_namlen(de)))
+ else if (rlen < UFS_DIR_REC_LEN(ufs_get_de_namlen(de)))
error_msg = "reclen is too small for namlen";
- else if (dir && ((char *) de - bh->b_data) + SWAB16(de->d_reclen) >
- dir->i_sb->s_blocksize)
+ else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
error_msg = "directory entry across blocks";
- else if (dir && SWAB32(de->d_ino) > (sb->u.ufs_sb.s_uspi->s_ipg * sb->u.ufs_sb.s_uspi->s_ncg))
+ else if (SWAB32(de->d_ino) > (sb->u.ufs_sb.s_uspi->s_ipg *
+ sb->u.ufs_sb.s_uspi->s_ncg))
error_msg = "inode out of bounds";

if (error_msg != NULL)
@@ -175,8 +176,8 @@
"offset=%lu, inode=%lu, reclen=%d, namlen=%d",
dir->i_ino, dir->i_size, error_msg, offset,
(unsigned long) SWAB32(de->d_ino),
- SWAB16(de->d_reclen), ufs_get_de_namlen(de));
-
+ rlen, ufs_get_de_namlen(de));
+
return (error_msg == NULL ? 1 : 0);
}

diff -ru linux-2.4.5.orig/fs/ufs/super.c linux-2.4.5-aed/fs/ufs/super.c
--- linux-2.4.5.orig/fs/ufs/super.c Tue May 29 13:13:21 2001
+++ linux-2.4.5-aed/fs/ufs/super.c Tue May 29 20:14:02 2001
@@ -265,6 +265,10 @@
*value++ = 0;
if (!strcmp (this_char, "ufstype")) {
ufs_clear_opt (*mount_options, UFSTYPE);
+ if (!value || !*value) {
+ printk ("UFS-fs: ufstype option needs value\n");
+ return 0;
+ }
if (!strcmp (value, "old"))
ufs_set_opt (*mount_options, UFSTYPE_OLD);
else if (!strcmp (value, "sun"))
@@ -288,6 +292,10 @@
}
else if (!strcmp (this_char, "onerror")) {
ufs_clear_opt (*mount_options, ONERROR);
+ if (!value || !*value) {
+ printk ("UFS-fs: onerror option needs value\n");
+ return 0;
+ }
if (!strcmp (value, "panic"))
ufs_set_opt (*mount_options, ONERROR_PANIC);
else if (!strcmp (value, "lock"))
--
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert
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