| Message ID | 20170807105701.3835991-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
On Monday, August 7, 2017 4:26:51 PM IST Arnd Bergmann wrote: > As Stefan pointed out, I misremembered what clang can do specifically, > and it turns out that the variable-length array at the end of the > structure did not work (a flexible array would have worked here > but not solved the problem): > > fs/ext4/mballoc.c:2303:17: error: fields must have a constant size: > 'variable length array in structure' extension will never be supported > ext4_grpblk_t counters[blocksize_bits + 2]; > > This reverts part of my previous patch, using a fixed-size array > again, but keeping the check for the array overflow. > > Fixes: 2df2c3402fc8 ("ext4: fix warning about stack corruption") > Reported-by: Stefan Agner <stefan@agner.ch> > Signed-off-by: Arnd Bergmann <arnd@arndb.de> I executed xfstests on a ppc64 machine with both 4k and 64k block size combination. Tested-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> -- chandan
On Sat, Aug 12, 2017 at 02:09:29PM +0530, Chandan Rajendra wrote: > On Monday, August 7, 2017 4:26:51 PM IST Arnd Bergmann wrote: > > As Stefan pointed out, I misremembered what clang can do specifically, > > and it turns out that the variable-length array at the end of the > > structure did not work (a flexible array would have worked here > > but not solved the problem): > > > > fs/ext4/mballoc.c:2303:17: error: fields must have a constant size: > > 'variable length array in structure' extension will never be supported > > ext4_grpblk_t counters[blocksize_bits + 2]; > > > > This reverts part of my previous patch, using a fixed-size array > > again, but keeping the check for the array overflow. > > > > Fixes: 2df2c3402fc8 ("ext4: fix warning about stack corruption") > > Reported-by: Stefan Agner <stefan@agner.ch> > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > I executed xfstests on a ppc64 machine with both 4k and 64k block size > combination. > > Tested-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> Thanks, applied. - Ted
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 5a1052627a81..701085620cd8 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -2300,7 +2300,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v) EXT4_MAX_BLOCK_LOG_SIZE); struct sg { struct ext4_group_info info; - ext4_grpblk_t counters[blocksize_bits + 2]; + ext4_grpblk_t counters[EXT4_MAX_BLOCK_LOG_SIZE + 2]; } sg; group--; @@ -2309,6 +2309,9 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v) " 2^0 2^1 2^2 2^3 2^4 2^5 2^6 " " 2^7 2^8 2^9 2^10 2^11 2^12 2^13 ]\n"); + i = (blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) + + sizeof(struct ext4_group_info); + grinfo = ext4_get_group_info(sb, group); /* Load the group info in memory only if not already loaded. */ if (unlikely(EXT4_MB_GRP_NEED_INIT(grinfo))) { @@ -2320,7 +2323,7 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v) buddy_loaded = 1; } - memcpy(&sg, ext4_get_group_info(sb, group), sizeof(sg)); + memcpy(&sg, ext4_get_group_info(sb, group), i); if (buddy_loaded) ext4_mb_unload_buddy(&e4b);
As Stefan pointed out, I misremembered what clang can do specifically, and it turns out that the variable-length array at the end of the structure did not work (a flexible array would have worked here but not solved the problem): fs/ext4/mballoc.c:2303:17: error: fields must have a constant size: 'variable length array in structure' extension will never be supported ext4_grpblk_t counters[blocksize_bits + 2]; This reverts part of my previous patch, using a fixed-size array again, but keeping the check for the array overflow. Fixes: 2df2c3402fc8 ("ext4: fix warning about stack corruption") Reported-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- fs/ext4/mballoc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) -- 2.9.0