Brüns, Stefan (Stefan.Bruens@rwth-aachen.de) wrote:
Doing unaligned reads is not supported on all architectures, use byte sized reads of the little endian buffer. Rename off16 to off8, as it reflects the buffer offset in byte granularity (offset is in entry, i.e. 12 bit, granularity). Fix a regression introduced in 8d48c92b45aea91e2a2be90f2ed93677e85526f1
Reported-by: Oleksandr Tymoshenko gonzo@bluezbox.com Signed-off-by: Stefan Brüns stefan.bruens@rwth-aachen.de
fs/fat/fat.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/fat/fat.c b/fs/fat/fat.c index fe899d0442..06088e2421 100644 --- a/fs/fat/fat.c +++ b/fs/fat/fat.c @@ -179,7 +179,7 @@ int flush_dirty_fat_buffer(fsdata *mydata) static __u32 get_fatent(fsdata *mydata, __u32 entry) { __u32 bufnum;
- __u32 off16, offset;
__u32 offset, off8; __u32 ret = 0x00;
if (CHECK_CLUST(entry, mydata->fatsize)) {
@@ -242,8 +242,9 @@ static __u32 get_fatent(fsdata *mydata, __u32 entry) ret = FAT2CPU16(((__u16 *) mydata->fatbuf)[offset]); break; case 12:
off16 = (offset * 3) / 2;ret = FAT2CPU16(*(__u16 *)(mydata->fatbuf + off16));
off8 = (offset * 3) / 2;/* fatbut + off8 may be unaligned, read in byte granularity */ret = mydata->fatbuf[off8] + mydata->fatbuf[off8 + 1] << 8;
This patch when applied gives me "Invalid FAT entry" message. Reason is: operator '<<' has lower precedence than '+' so this expression is equivalent to (mydata->fatbuf[off8] + mydata->fatbuf[off8 + 1]) << 8 With explicit parentheses around shift it works as expected:
ret = mydata->fatbuf[off8] + (mydata->fatbuf[off8 + 1] << 8);