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udf: Avoid infinite loop when processing indirect ICBs

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We did not implement any bound on number of indirect ICBs we follow when
loading inode. Thus corrupted medium could cause kernel to go into an
infinite loop, possibly causing a stack overflow.

Fix the possible stack overflow by removing recursion from
__udf_read_inode() and limit number of indirect ICBs we follow to avoid
infinite loops.

Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara 2014-09-04 14:06:55 +02:00
parent bb7720a0b4
commit c03aa9f6e1
1 changed files with 21 additions and 14 deletions
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35
fs/udf/inode.c
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@ -1270,6 +1270,13 @@ int udf_setsize(struct inode *inode, loff_t newsize)
return 0;
}
/*
* Maximum length of linked list formed by ICB hierarchy. The chosen number is
* arbitrary - just that we hopefully don't limit any real use of rewritten
* inode on write-once media but avoid looping for too long on corrupted media.
*/
#define UDF_MAX_ICB_NESTING 1024
static void __udf_read_inode(struct inode *inode)
{
struct buffer_head *bh = NULL;
@ -1279,7 +1286,9 @@ static void __udf_read_inode(struct inode *inode)
struct udf_inode_info *iinfo = UDF_I(inode);
struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
unsigned int link_count;
unsigned int indirections = 0;
reread:
/*
* Set defaults, but the inode is still incomplete!
* Note: get_new_inode() sets the following on a new inode:
@ -1317,28 +1326,26 @@ static void __udf_read_inode(struct inode *inode)
ibh = udf_read_ptagged(inode->i_sb, &iinfo->i_location, 1,
&ident);
if (ident == TAG_IDENT_IE && ibh) {
struct buffer_head *nbh = NULL;
struct kernel_lb_addr loc;
struct indirectEntry *ie;
ie = (struct indirectEntry *)ibh->b_data;
loc = lelb_to_cpu(ie->indirectICB.extLocation);
if (ie->indirectICB.extLength &&
(nbh = udf_read_ptagged(inode->i_sb, &loc, 0,
&ident))) {
if (ident == TAG_IDENT_FE ||
ident == TAG_IDENT_EFE) {
memcpy(&iinfo->i_location,
&loc,
sizeof(struct kernel_lb_addr));
brelse(bh);
brelse(ibh);
brelse(nbh);
__udf_read_inode(inode);
if (ie->indirectICB.extLength) {
brelse(bh);
brelse(ibh);
memcpy(&iinfo->i_location, &loc,
sizeof(struct kernel_lb_addr));
if (++indirections > UDF_MAX_ICB_NESTING) {
udf_err(inode->i_sb,
"too many ICBs in ICB hierarchy"
" (max %d supported)\n",
UDF_MAX_ICB_NESTING);
make_bad_inode(inode);
return;
}
brelse(nbh);
goto reread;
}
}
brelse(ibh);