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| author | Solomon Peachy <pizza@shaftnet.org> | 2020-07-11 16:22:21 -0400 |
|---|---|---|
| committer | Solomon Peachy <pizza@shaftnet.org> | 2020-07-11 18:23:46 -0400 |
| commit | 7249fabe63b6106225c11c401fdc17cd4b03ad5e (patch) | |
| tree | 4d30a09ee2813d3f5703f26dc9cb676c4f002536 | |
| parent | aa20b6af7a860bc40662e141c12fec098048b8c0 (diff) | |
| download | rockbox-7249fabe63b6106225c11c401fdc17cd4b03ad5e.tar.gz rockbox-7249fabe63b6106225c11c401fdc17cd4b03ad5e.zip | |
fat: Validate FS Info Sector signature when attempting to mount volume
The "try to mount as superfloppy" fails with some partitioning layouts
because sector 0 can have a mostly-valid FAT32 signature. However, in
all dumps I've looked at, sector 0's fsinfo offset value points at a place
which lacks the fsinfo signature.
Resolves FS#13213, no known regressions.
Change-Id: Ib323d35cca6ca54e11aca6ba77041bf33a05a277
| -rw-r--r-- | firmware/drivers/fat.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/firmware/drivers/fat.c b/firmware/drivers/fat.c index b14e461a65..cc6dbf517c 100644 --- a/firmware/drivers/fat.c +++ b/firmware/drivers/fat.c @@ -178,9 +178,12 @@ struct fsinfo clusters, or 0xffffffff for no hint */ }; /* fsinfo offsets */ +#define FSINFO_SIGNATURE 0 #define FSINFO_FREECOUNT 488 #define FSINFO_NEXTFREE 492 +#define FSINFO_SIGNATURE_VAL 0x41615252 + #ifdef HAVE_FAT16SUPPORT #define BPB_FN_SET16(bpb, fn) (bpb)->fn##__ = fn##16 #define BPB_FN_SET32(bpb, fn) (bpb)->fn##__ = fn##32 @@ -1251,6 +1254,14 @@ static int fat_mount_internal(struct bpb *fat_bpb) FAT_ERROR(rc * 10 - 8); } + /* Sanity check FS info */ + long info = BYTES2INT32(buf, FSINFO_SIGNATURE); + if (info != FSINFO_SIGNATURE_VAL) { + DEBUGF("%S() FSInfo signature mismatch (%x)\n", + __func__, info); + FAT_ERROR(-9); + } + fat_bpb->fsinfo.freecount = BYTES2INT32(buf, FSINFO_FREECOUNT); fat_bpb->fsinfo.nextfree = BYTES2INT32(buf, FSINFO_NEXTFREE); } |