Joseph Qi
2018-Mar-30 01:26 UTC
[Ocfs2-devel] [PATCH] ocfs2: don't evaluate buffer head to NULL managed by caller
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.changwei at 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; > } > } >
Changwei Ge
2018-Mar-30 01:31 UTC
[Ocfs2-devel] [PATCH] ocfs2: don't evaluate buffer head to NULL managed by caller
Hi Joseph, On 2018/3/30 9:27, Joseph Qi wrote:> > > 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.changwei at 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 for your review. Yes, we will only put bh internally allocated. If bh is reserved in advance, we will not put it and re-assign it to NULL. Thanks, Changwei> > 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; >> } >> } >> >
piaojun
2018-Mar-30 02:16 UTC
[Ocfs2-devel] [PATCH] ocfs2: don't evaluate buffer head to NULL managed by caller
Hi Joseph and Changwei, On 2018/3/30 9:26, Joseph Qi wrote:> > > 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.changwei at 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?I think this branch will put bh external allocated as 'new_bh' only means bhs[0] is internal allocated. So this branch seems inappropriate. thanks, Jun> > 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; >> } >> } >> > . >