From: Gao Xiang Date: Tue, 16 Sep 2025 08:48:51 +0000 (+0800) Subject: erofs: avoid reading more for fragment maps X-Git-Tag: v6.18-rc1~223^2~2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=334c0e493c2aa3e843a80bb9f3862bb50360cb36;p=thirdparty%2Flinux.git erofs: avoid reading more for fragment maps Since all real encoded extents (directly handled by the decompression subsystem) have a sane, limited maximum decoded length (Z_EROFS_PCLUSTER_MAX_DSIZE), and the read-more policy is only applied if needed. However, it makes no sense to read more for non-encoded maps, such as fragment extents, since such extents can be huge (up to i_size) and there is no benefit to reading more at this layer. For normal images, it does not really matter, but for crafted images generated by syzbot, excessively large fragment extents can cause read-more to run for an overly long time. Reported-and-tested-by: syzbot+1a9af3ef3c84c5e14dcc@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/68c8583d.050a0220.2ff435.03a3.GAE@google.com Fixes: b44686c8391b ("erofs: fix large fragment handling") Fixes: b15b2e307c3a ("erofs: support on-disk compressed fragments data") Reviewed-by: Hongbo Li Reviewed-by: Chao Yu Signed-off-by: Gao Xiang --- diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 2d73297003d25..625b8ae8f67f0 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -1835,7 +1835,7 @@ static void z_erofs_pcluster_readmore(struct z_erofs_frontend *f, map->m_la = end; err = z_erofs_map_blocks_iter(inode, map, EROFS_GET_BLOCKS_READMORE); - if (err) + if (err || !(map->m_flags & EROFS_MAP_ENCODED)) return; /* expand ra for the trailing edge if readahead */ @@ -1847,7 +1847,7 @@ static void z_erofs_pcluster_readmore(struct z_erofs_frontend *f, end = round_up(end, PAGE_SIZE); } else { end = round_up(map->m_la, PAGE_SIZE); - if (!map->m_llen) + if (!(map->m_flags & EROFS_MAP_ENCODED) || !map->m_llen) return; }