From c03aa9f6e1f938618e6db2e23afef0574efeeb65 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 4 Sep 2014 14:06:55 +0200 Subject: [PATCH] udf: Avoid infinite loop when processing indirect ICBs 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 --- fs/udf/inode.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/fs/udf/inode.c b/fs/udf/inode.c index 68cc7b144c26..a6a40536ebf1 100644 --- a/fs/udf/inode.c +++ b/fs/udf/inode.c @@ -1270,6 +1270,13 @@ update_time: 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); -- 2.20.1