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erofs: fix incorrect symlink detection in fast symlink

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commit 9ed50b8231e37b1ae863f5dec8153b98d9f389b4 upstream.

Fast symlink can be used if the on-disk symlink data is stored
in the same block as the on-disk inode, so we don’t need to trigger
another I/O for symlink data.  However, currently fs correction could be
reported _incorrectly_ if inode xattrs are too large.

In fact, these should be valid images although they cannot be handled as
fast symlinks.

Many thanks to Colin for reporting this!

Reported-by: Colin Walters <walters@verbum.org>
Reported-by: https://honggfuzz.dev/
Link: https://lore.kernel.org/r/bb2dd430-7de0-47da-ae5b-82ab2dd4d945@app.fastmail.com
Fixes: 431339ba9042 ("staging: erofs: add inode operations")
[ Note that it's a runtime misbehavior instead of a security issue. ]
Link: https://lore.kernel.org/r/20240909031911.1174718-1-hsiangkao@linux.alibaba.com
[ Gao Xiang: fix 5.10.y build warning due to `check_add_overflow`. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Gao Xiang 2024-12-18 15:36:26 +08:00 committed by Greg Kroah-Hartman
parent 0ab621fcdf
commit 7678451d66
1 changed files with 6 additions and 14 deletions
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20
fs/erofs/inode.c
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@ -198,11 +198,14 @@ static int erofs_fill_symlink(struct inode *inode, void *data,
unsigned int m_pofs)
{
struct erofs_inode *vi = EROFS_I(inode);
loff_t off;
char *lnk;
/* if it cannot be handled with fast symlink scheme */
if (vi->datalayout != EROFS_INODE_FLAT_INLINE ||
inode->i_size >= PAGE_SIZE || inode->i_size < 0) {
m_pofs += vi->xattr_isize;
/* check if it cannot be handled with fast symlink scheme */
if (vi->datalayout != EROFS_INODE_FLAT_INLINE || inode->i_size < 0 ||
check_add_overflow((loff_t)m_pofs, inode->i_size, &off) ||
off > i_blocksize(inode)) {
inode->i_op = &erofs_symlink_iops;
return 0;
}
@ -211,17 +214,6 @@ static int erofs_fill_symlink(struct inode *inode, void *data,
if (!lnk)
return -ENOMEM;
m_pofs += vi->xattr_isize;
/* inline symlink data shouldn't cross page boundary as well */
if (m_pofs + inode->i_size > PAGE_SIZE) {
kfree(lnk);
erofs_err(inode->i_sb,
"inline data cross block boundary @ nid %llu",
vi->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
memcpy(lnk, data + m_pofs, inode->i_size);
lnk[inode->i_size] = '\0';