Re: [PATCH -next 1/2] ext4: fix potential memory leak in ext4_fc_record_regions()

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Hello,

Le 20/09/2022 à 03:07, yebin a écrit :


On 2022/9/20 2:40, Damien Guibouret wrote:
Hello,

Le 19/09/2022 à 16:40, Ye Bin a écrit :
As krealloc may return NULL, in this case 'state->fc_regions' may not be
freed by krealloc, but 'state->fc_regions' already set NULL. Then will
lead to 'state->fc_regions' memory leak.

Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
  fs/ext4/fast_commit.c | 14 ++++++++------
  1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
index 9217a588afd1..cc8c8db075ba 100644
--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -1677,15 +1677,17 @@ int ext4_fc_record_regions(struct super_block *sb, int ino,
      if (replay && state->fc_regions_used != state->fc_regions_valid)
          state->fc_regions_used = state->fc_regions_valid;
      if (state->fc_regions_used == state->fc_regions_size) {
+        struct ext4_fc_alloc_region *fc_regions;
+
          state->fc_regions_size +=
              EXT4_FC_REPLAY_REALLOC_INCREMENT;
-        state->fc_regions = krealloc(
-                    state->fc_regions,
-                    state->fc_regions_size *
-                    sizeof(struct ext4_fc_alloc_region),
-                    GFP_KERNEL);
-        if (!state->fc_regions)
+        fc_regions = krealloc(state->fc_regions,
+                      state->fc_regions_size *
+                      sizeof(struct ext4_fc_alloc_region),
+                      GFP_KERNEL);
+        if (!fc_regions)

Would it not be safer to restore state->fc_regions_size to its previous value in that case to keep consistency between size value and allocated size (or to update state->fc_regions_size only after allocation as it is done in second part of this patch) ?

Actually, If   'ext4_fc_record_regions()' return -ENOMEM, then will stop replay journal.
'state->fc_regions_size' will not be used any more, so it's safe.

There are at least two calls in ext4_ext_clear_bb (ext4/extents.c) that do not check for return code of ext4_fc_record_regions. But perhaps these are these calls that should be fixed.

              return -ENOMEM;
+        state->fc_regions = fc_regions;
      }
      region = &state->fc_regions[state->fc_regions_used++];
      region->ino = ino;


Regards,

Damien




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