From 425aa3c6944dc7f52a68d153e9caebf3f861826f Mon Sep 17 00:00:00 2001 From: Christopher Haster Date: Wed, 27 Dec 2017 10:44:40 -0600 Subject: [PATCH] Fixed issue with immediate exhaustion and small unaligned storage This was a small hole in the logic that handles initializing the lookahead buffer. To imitate exhaustion (so the block allocator will trigger a scan), the lookahead buffer is rewound a full lookahead and set up to look like it is exhausted. However, unlike normal allocation, this rewind was not kept aligned to a multiple of the scan size, which is limited by both the lookahead buffer and the total storage size. This bug went unnoticed for so long because it only causes problems when the block device is both: 1. Not aligned to the lookahead buffer (not a power of 2) 2. Smaller than the lookahead buffer While this seems like a strange corner case for a block device, this turned out to be very common for internal flash, especially when a handleful of blocks are reserved for code. --- .travis.yml | 7 +++---- lfs.c | 4 ++-- 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/.travis.yml b/.travis.yml index d673c15..c17af8b 100644 --- a/.travis.yml +++ b/.travis.yml @@ -12,10 +12,9 @@ script: - make test QUIET=1 # run tests with a few different configurations - - CFLAGS="-DLFS_READ_SIZE=1 -DLFS_PROG_SIZE=1" make test QUIET=1 - - CFLAGS="-DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512" make test QUIET=1 - - CFLAGS="-DLFS_BLOCK_COUNT=1023" make test QUIET=1 - - CFLAGS="-DLFS_LOOKAHEAD=2048" make test QUIET=1 + - CFLAGS="-DLFS_READ_SIZE=1 -DLFS_PROG_SIZE=1" make test QUIET=1 + - CFLAGS="-DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512" make test QUIET=1 + - CFLAGS="-DLFS_BLOCK_COUNT=1023 -DLFS_LOOKAHEAD=2048" make test QUIET=1 # self-host with littlefs-fuse for fuzz test - make -C littlefs-fuse diff --git a/lfs.c b/lfs.c index ea116d2..2d0e331 100644 --- a/lfs.c +++ b/lfs.c @@ -2040,8 +2040,8 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) { } // setup free lookahead - lfs->free.begin = -lfs->cfg->lookahead; - lfs->free.off = lfs->cfg->lookahead; + lfs->free.begin = -lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count); + lfs->free.off = -lfs->free.begin; lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count; // load superblock