From db2efc9e0a8cdb70afc8dd7c9621da9376da7afb Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Thu, 26 Dec 2019 23:19:54 -0500 Subject: [PATCH 01/46] libext2fs: fix crash in ext2fs_open2() on Big Endian systems Content-Type: text/plain Commit e6069a05: ("Teach ext2fs_open2() to honor the EXT2_FLAG_SUPER_ONLY flag") changed how the function ext2fs_group_desc() handled a request for a gdp pointer for a group larger than the number of groups in the file system; it now returns NULL, instead of returning a pointer beyond the end of the array. Previously, the ext2fs_open2() function would swap all of the block group descriptors in a block, even if they are beyond the end of the file system. This was OK, since we were not overrunning the allocated memory, since it was rounded to a block boundary. But now that ext2fs_group_desc() would return NULL for those gdp, it would cause ext2fs_open2(), when it was byte swapping the block group descriptors on Big Endian systems, to dereference a null pointer and crash. This commit adds a NULL pointer check to avoid byte swapping those block group descriptors in a bg descriptor block, but which are beyond the end of the file system, to address this crash. Signed-off-by: Theodore Ts'o Reported-by: Anatoly Pugachev Signed-off-by: Lukas Czerner --- lib/ext2fs/openfs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c index 51b54a44..e457ce1a 100644 --- a/lib/ext2fs/openfs.c +++ b/lib/ext2fs/openfs.c @@ -433,7 +433,8 @@ errcode_t ext2fs_open2(const char *name, const char *io_options, gdp = (struct ext2_group_desc *) dest; for (j=0; j < groups_per_block*first_meta_bg; j++) { gdp = ext2fs_group_desc(fs, fs->group_desc, j); - ext2fs_swap_group_desc2(fs, gdp); + if (gdp) + ext2fs_swap_group_desc2(fs, gdp); } #endif dest += fs->blocksize*first_meta_bg; @@ -453,7 +454,8 @@ errcode_t ext2fs_open2(const char *name, const char *io_options, for (j=0; j < groups_per_block; j++) { gdp = ext2fs_group_desc(fs, fs->group_desc, i * groups_per_block + j); - ext2fs_swap_group_desc2(fs, gdp); + if (gdp) + ext2fs_swap_group_desc2(fs, gdp); } #endif dest += fs->blocksize; -- 2.35.1