On 18/3/29 10:06, Changwei Ge wrote: > ocfs2_read_blocks() is used to read several blocks from disk. > Currently, the input argument *bhs* can be NULL or NOT. It depends on > the caller's behavior. If the function fails in reading blocks from > disk, the corresponding bh will be assigned to NULL and put. > > Obviously, above process for non-NULL input bh is not appropriate. > Because the caller doesn't even know its bhs are put and re-assigned. > > If buffer head is managed by caller, ocfs2_read_blocks should not > evaluate it to NULL. It will cause caller accessing illegal memory, > thus crash. > > Signed-off-by: Changwei Ge <ge.chang...@h3c.com> > --- > fs/ocfs2/buffer_head_io.c | 31 +++++++++++++++++++++++++------ > 1 file changed, 25 insertions(+), 6 deletions(-) > > diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c > index d9ebe11..17329b6 100644 > --- a/fs/ocfs2/buffer_head_io.c > +++ b/fs/ocfs2/buffer_head_io.c > @@ -188,6 +188,7 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 > block, int nr, > int i, ignore_cache = 0; > struct buffer_head *bh; > struct super_block *sb = ocfs2_metadata_cache_get_super(ci); > + int new_bh = 0; > > trace_ocfs2_read_blocks_begin(ci, (unsigned long long)block, nr, flags); > > @@ -213,6 +214,18 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 > block, int nr, > goto bail; > } > > + /* Use below trick to check if all bhs are NULL or assigned. > + * Basically, we hope all bhs are consistent so that we can > + * handle exception easily. > + */ > + new_bh = (bhs[0] == NULL); > + for (i = 1 ; i < nr ; i++) { > + if ((new_bh && bhs[i]) || (!new_bh && !bhs[i])) { > + WARN(1, "Not all bhs are consistent\n"); > + break; > + } > + } > + > ocfs2_metadata_cache_io_lock(ci); > for (i = 0 ; i < nr ; i++) { > if (bhs[i] == NULL) { > @@ -324,8 +337,10 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 > block, int nr, > if (!(flags & OCFS2_BH_READAHEAD)) { > if (status) { > /* Clear the rest of the buffers on error */ > - put_bh(bh); > - bhs[i] = NULL; > + if (new_bh) { > + put_bh(bh); > + bhs[i] = NULL; > + }
Since we assume caller has to pass either all NULL or all non-NULL, here we will only put bh internal allocated. Am I missing something? Thanks, Joseph > continue; > } > /* We know this can't have changed as we hold the > @@ -342,8 +357,10 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 > block, int nr, > * for this bh as it's not marked locally > * uptodate. */ > status = -EIO; > - put_bh(bh); > - bhs[i] = NULL; > + if (new_bh) { > + put_bh(bh); > + bhs[i] = NULL; > + } > continue; > } > > @@ -355,8 +372,10 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 > block, int nr, > clear_buffer_needs_validate(bh); > status = validate(sb, bh); > if (status) { > - put_bh(bh); > - bhs[i] = NULL; > + if (new_bh) { > + put_bh(bh); > + bhs[i] = NULL; > + } > continue; > } > } > _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel